Not sure it is the same for everybody.
If I start with an empty stomach it typically takes me about 3-4 enemas to get to a clear return. More than 4 is frustrating because it rags me out, but I do what I need to do to meet my goal of a clear return.
Understand this: The stomach empties part of it's content into the small intestine about every 15 minutes. Likewise the small intestine releases part of it's content to the large intestine at a similar interval but almost never in sync with what happens above.
This is why I start most eenema sessions with 30mg oral bisacodyl. I then wait about 2 hours before taking the first round of the enema.
I also make sure to retain the enema 15 minutes. The release does not come all at once. It takes 20-30 minutes to get it to expel. I let my body tell me how much recovery time between rounds, but my average is about 1 round per hour. That is average across the session and NOT a hard and fast rule.
Bisacodyl works only on the large intestine and the hardest part to clear out is the small intestine It usually but not always "kicks in" and with that much bisacodyl it is truly a "kick" between the second and third enema.
One thing that DOES help get to a clear return:
Between rounds of expulsion take 1-1/2 times the normal dose of Milk of Magnesia. Start as the first enema is expelling and do it each round as you expel. If you find this helps you, drink all the water you can between rounds. You will know when the MOM has gone to work because the smell will change.
Let us know what works for you!