I'm pretty sure it has to be a fractional percentage. full % values trigger an IFT.
I just did my first yesterday, then tried to do adjust my round # percentage values, and it kicked me as an IFT.
Tonite after the close, (tomorrow a.m. actually) I will adjust the resulting fractionals from today's market up or down to rebalance, that will IFT COB Friday.
Monday's #'s will be round, so my next 1% move would be Tues COB, after Monday's market creates fractional results I can reallocate to round percentages.
I suppose theoretically, moves of 15% could be made per month, since it appears you have to wait 1 day after your round # rebalance occurs to obtain your fractional gains/loss of the post IFT trading day, then IFT again.