A control device comprising: a controller configured to perform: (a) acquiring an index value from a recording device at an acquisition timing, the recording device including: a mounting case in which a cartridge accommodating a printing agent is mountable; a tank configured to accommodate the printing agent supplied from the cartridge; and a recording portion configured to record an image on a sheet with the printing agent supplied from the tank, the index value being acquired under a condition where a first cartridge is mounted in the mounting case of the recording device, the index value being representative of a residual quantity of the printing agent remaining in the first cartridge and the tank at the acquisition timing; (b) storing the index value in association with timing information about the acquisition timing in a memory; (c) setting, after performing the (a) acquiring and the (b) storing a plurality of number of times and storing a plurality of index values in the memory in association with a plurality of sets of timing information, an order condition using the plurality of sets of timing information and the plurality of index values stored in the memory, the plurality of index values including a latest index value acquired at a latest acquisition timing, the order condition requiring that one of the latest index value and a current timing have reached corresponding one of a reference index value and a reference timing, the order condition being set so that a second cartridge ordered for replacement with the first cartridge is delivered to a predetermined destination at a first timing by assuming that a time interval between the reference timing and the first timing is a first period of time, the first timing being a timing at which the first cartridge is expected to be out of the printing agent while the tank is expected to still accommodate the printing agent, the first period of time being an expected period of time from when the second cartridge has been ordered to when the second cartridge has been delivered to the predetermined destination; and (d) transmitting an order command to a relevant device after the order condition is satisfied, the order command instructing to order the second cartridge. (a) acquiring an index value from a recording device at an acquisition timing, the recording device including: a mounting case in which a cartridge accommodating a printing agent is mountable; a tank configured to accommodate the printing agent supplied from the cartridge; and a recording portion configured to record an image on a sheet with the printing agent supplied from the tank, the index value being acquired under a condition where a first cartridge is mounted in the mounting case of the recording device, the index value being representative of a residual quantity of the printing agent remaining in the first cartridge and the tank at the acquisition timing; (b) storing the index value in association with timing information about the acquisition timing in a memory; (c) setting, after performing the (a) acquiring and the (b) storing a plurality of number of times and storing a plurality of index values in the memory in association with a plurality of sets of timing information, an order condition using the plurality of sets of timing information and the plurality of index values stored in the memory, the plurality of index values including a latest index value acquired at a latest acquisition timing, the order condition requiring that one of the latest index value and a current timing have reached corresponding one of a reference index value and a reference timing, the order condition being set so that a second cartridge ordered for replacement with the first cartridge is delivered to a predetermined destination at a first timing by assuming that a time interval between the reference timing and the first timing is a first period of time, the first timing being a timing at which the first cartridge is expected to be out of the printing agent while the tank is expected to still accommodate the printing agent, the first period of time being an expected period of time from when the second cartridge has been ordered to when the second cartridge has been delivered to the predetermined destination; and (d) transmitting an order command to a relevant device after the order condition is satisfied, the order command instructing to order the second cartridge.