PSF change question

[MakaveliX]

Have a 2002 C240 Mercedes and I fancied doing a PSF fluid change as follows ( the level according to the dipstick was right at the min mark )

Use a pela pump to extract as much fluid as I could ( I had to go full left and full right lock with the engine off to get as much out as possible )
I measured exactly how much came out at 650ML

Tried to put in 650ML and ended up getting to about 400ML and then the reservoir was full and nearly spilling out, this is where I got confused. At this point are you supposed to turn the engine on and then steer a few times to get it to go round the system? Makes no sense how I couldn't put back in what came out.

Eventually with trial and error I took some out, put some back in etc and now the levels are spot on. There is a cold reading which is now in the right place, and after a drive the warm reading is also correct so I got there in the end. ( Also bled air out the system by turning on the engine with the reservoir cap off and doing some lock to lock steering.

So question is. when refilling PSF, should you periodically turn the engine on and steer a bit so that you can put in the required amount ?

[E-bmw]

If you emptied it by turning R/L to get the system empty, you need to do the same to fill as the pump/hoses are basically empty of oil/full of air which needs to be displaced by your fresh fluid.

So, yes is the answer.