Hi,
1) As i understood, i think instead of Compensatory off (PH) you might have booked attendance type Compensatory Off (Normal) kindly check once again if it is't let me know.
2) Normally Com off and OT both scenarios are different, For OT SAP standard system will support through TO01,TO02 (PCR's) please refer both pcr's.
3) It will't com under com.off scenario it will come under absence quota scenario because com off is nothing but if employee will work on week off he/she can eligible for any week day off that is also you should maintain attendance type other wise how system will come to know whether he/she came or not?
Yours
Mohan