Table:
|  | January 31, 2019 |  | January 31, 2018 |
| --- | --- | --- | --- |
| (in millions) | ASC 606 | ASC 605 | ASC 605 |
| Deferred revenue | $2,091.4 | $2,269.2 | $1,955.1 |
| Unbilled deferred revenue | 591.0 | 491.6 | 326.4 |
| Total deferred revenue | $2,682.4 | $2,760.8 | $2,281.5 |
Paragraphs:
Total Deferred Revenue
The adoption of ASC Topic 606 required a change to the definition of unbilled deferred revenue and new qualitative and quantitative disclosures around our performance obligations. Unbilled deferred revenue represents contractually stated or committed orders under early renewal and multi-year billing plans primarily for subscription, services and maintenance for which the associated deferred revenue has not been recognized. Under ASC Topic 606, unbilled deferred revenue is not included as a receivable or deferred revenue on our Consolidated Balance Sheet. See Part II, Item 8, Note 2, “Revenue Recognition” for more details on Autodesk's performance obligations.
We expect that the amount of billed and unbilled deferred revenue will change from quarter to quarter for several reasons, including the specific timing, duration and size of customer subscription and support agreements, varying billing cycles of such agreements, the specific timing of customer renewals, and foreign currency fluctuations
Question:
What is the difference between the unbilled deferred revenue for ASC 605 from January 31, 2018 to January 31, 2019?
Answer: 491.6-326.4  = 165.2