I just spent a week flushing out the cooling system on a Ford Focus..............
First 3 flushes I captured and just did a idle warm up. (Then took anti-freeze to hazardous waste)
Then I'd fill with water, drive a day, drain at night; for 3 days. (I'd just dump the 'water' on a bush)
Then I added the flushing chemicals and did 4 hours of driving.
Then 4 more water flushes.
Then compute how much full strength anti-freeze I need to get 50/50 mixture given cooling capacity. (there's always water left in the block, so 50/50 will be diluted). Top off with water.
The first three flushes I take it you only used water?