No, I dividend between 16 waking hours - it's a pretty easy calculation: 16x3=48, which is within the range of 40-60.
If the person did it every 15 minutes it'd be 64 times during waking hours, but I felt that "roughly 20 minutes" suffices for a time range of 16-20 minutes •́ ‿ , •̀
I'm thinking of this for someone working in an office situation. Depending on how long it takes to perform the enema, this is about the same schedule as smokers. So maybe it's not so far off??
Then again, I'm guessing you divided that by 24 hours rather than a work day. Once per 20 minutes would me no sleep which would have worse health effects