3 Revenue and other income (continued)
(b) Revenue recognition
AASB 15 establishes principles for reporting the nature, amount, timing, and uncertainty of revenue and cash flows arising from an entity’s contracts with customers and requires application of a five-step process to identify the contract with the customer, identify performance obligations in the contract, determine transaction price, allocate the transaction price to the performance obligations and recognise revenue when performance obligations are satisfied.
Revenue is recognised for the major business activities as follows:
(i) Data centre services
Data centre services revenue primarily consists of recurring monthly service fees and upfront project fees.
Revenue from the provision of recurring monthly service fees is recognised in the accounting period in which the services are rendered. Project fees are primarily comprised of installation services relating to a customer's initial deployment. As this is not considered to be a distinct service, revenue is deferred and recognised over the term of the contract with the customer, taking into account renewal options that are held by the customer. Upfront discounts provided to customers are contract assets that are amortised over the expected contract life - refer to Note 6(b).
The Group applies the practical expedient in the revenue standard and does not disclose information about the transaction price allocated to remaining performance obligations on contracts that are unsatisfied, as the Group has the right to consideration from its customers in an amount that corresponds directly with the value to the customer of the Group’s services to date. This is applied to all its data centre services revenue, on the basis that the upfront project fees are not a significant portion of each contract.
(ii) Interest income
Interest income is calculated by applying the effective interest rate to the gross carrying amount of a financial asset, except for financial assets that subsequently become credit-impaired. For credit-impaired financial assets, the effective interest rate is applied to the net carrying amount of the financial asset (after deduction of the loss allowance).
(iii) Distributions from investments
Distributions from investments are recognised as revenue when the right to receive payment is established.
The following disclosures relate to 30 June 2018 balances:
Revenue is measured at the fair value of the consideration received or receivable.
The Group recognises revenue when the amount of revenue can be reliably measured, it is probable that future economic benefits will flow to the entity and specific criteria have been met for each of the activities as described below. The Group bases its estimates on historical results, taking into consideration the type of customer, the type of transaction and the specifics of each arrangement.
Revenue is recognised for the major business activities as follows:
(iv) Data centre services
Revenue is recognised only when the service has been provided, the amount of revenue can be measured reliably and it is probable that the economic benefits associated with the transaction will flow to the Group. Upfront discounts provided to customers are amortised over the contract term.
(v) Interest income
Interest income is recognised using the effective interest method. When a receivable is impaired, the Group reduces the carrying amount to its recoverable amount, being the estimated future cash flow discounted at the original effective interest rate of the instrument, and continues unwinding the discount as interest income. Interest income on impaired loans is recognised using the original effective interest rate.
(vi) Distributions from investments
Distributions from investments are recognised as revenue when the right to receive payment is established.
Table:
 | 30 June 2019 | 30 June 2018
 | $'000 | $'000
FROM CONTINUING OPERATIONS |  | 
Data centre services revenue | 169,696 | 152,560
Interest income | 8,220 | 5,778
Distributions from investments | 1,344 | 3,191
Subtotal - other revenue | 9,564 | 8,969
Total revenue | 179,260 | 161,529
Gain on extinguishment of B1 lease | 1,068 | -
Gain on extinguishment of APDC leases | 1,291 | -
Other items included in gains | 675 | 284
Total Other income | 3,034 | 284


Question: What does the data centre services revenue consist of?
Answer: Recurring monthly service fees, Upfront project fees