Possible mistake when flushing coolant?
 

Hi all, hope someone out there smarter than me can set my mind at ease.

When I look in the manual it says the coolant system takes 7L of coolant. I just finished doing my first flush (3 drains) and at max I'd say each drain I did I'd only get roughly 4L of fluid. Anyone else have this issue? I'm concerned that flushing with distilled water then adding in the new coolant I've inadvertently mixed the 50/50 coolant with water still inside the system. I'm going to continue to monitor the engine temperature and keep an eye on the coolant levels over the next few days. I'm just concerned I somehow missed something.