Your query as it is written will only match records that have the exact same start and end date/times. I suspect that will rarely happen. Is that your intention? Or are you only wanting 5 created in the same window. I am having a hard time understanding a business case why you would want this, btw.
Maybe if you explain your use case, I can help you get the script right.
Also, there are some other things wrong with the script include. something like this would improve the logic, but your date query still needs to be addressed:
var gR = new GlideAggregate('incident');
gR.addAggregate('COUNT');
// change to GlideAggregate ^ for performance
gR.addActiveQuery();
// you can use addActiveQuery here ^
gs.log('inside incident table');
//gR.addQuery('u_call_back_date', days);
gR.addQuery('u_callback_start_date', starts);
gR.addQuery('u_callback_end_date', ends);
// we need to work on this part above because I don't think this is what you actually want ^
gR.query();
if(gR.next()) {
var count = gR.getAggregate('COUNT');
}
return count >= 5;
// this will now return a true or false, instead of yes or no.
