For 1000ml working solution you will need 100ml of Part A, 100 ml of Part B and 100ml of Part C + 10ml of Starter (adding one by one into 690ml of 49 C hot water). If you have all that in your set, you're ready to go and make yourself 1 liter of developer.

With 1 liter you can do even 25 rolls, no problem..