Hi sripathi,
take example 20MHZ BW FDD and CFI = MAX .i.e 3 , PHICH normal and NG = MIN i.e 1/6 . so there are 3600 R.E's in 20mhz 3 symbol PDCCH,
1 CCE = 36 R.E , so there are 3600/36 = 100 CCE, But first symbole will be occupied by reference signal , PHICH and PCFICH. in CELL ID 0.so only MAX of 87 CCE is possible out of 100 CCE . that is the reason FAPI have said only 0 - 88 is possible.