CURRENT-BAL PIC S9(13)V99 COMP-3
That declaration is indeed for an 8-byte PD field. So ON(302,08,PD,C4) would be correct. If it's NOT, then either the field does NOT start in position 302 or it does NOT actually match that declaration.
To find out, you can use ON(302,08,HEX) to see what the field really looks like in hex.