When the DELAY_FORMAT attribute is set to TIME mode, the DELAY_VALUE attribute represents an amount in ps. The IDELAYE3 has a clock/data align delay that is in addition to the DELAY_VALUE attribute. The total delay through the IDELAYE3 is the align delay plus the DELAY_VALUE.
Despite that in TIME mode the DELAY_VALUE represents a time value in ps, the value read or written from or to the delay line by the CNTVALUEIN[8:0] and/or CNTVALUEOU[8:0] is expressed in an amount of taps. So changing the time of a delay line requires some calculation, which is provided in the DELAY_MODE/VAR_LOAD paragraph.
When the DELAY_FORMAT attribute is set to COUNT mode, the DELAY_VALUE attribute represents an amount of taps. Because there is no calibration or compensation in COUNT mode, there is no Align_Delay for clock/data. Therefore the total through the IDELAYE3 is equal to the number of taps.