How many flowfiles you get after splitting?
But as example for your properties of your processor
If you get like 10 flowfiles
set 'minimum number of entries' to 1000 (like maximum)
and you have to set the 'minimum bin age' like 10 sec
So if the first flowfile comes in with attribute value ABC the flowfile gets hold and the 10 sec timer gets startet and if the next one comes in within the time it is in the same bin.
For every bin (in your case 3) the timer gets started for its own.
minimum number of entries gets ignored cause you set the minimum bin age