Okay, you're wanting to know why a FIXED BINARY field is not rounding to decimal rules? Probably because it is rounding to binary rules.
16.8750 = 10000.111 in binary. Rounding to 2 binary digits (which is what you are telling it to do) adds .001 (1/2 of the last round digit) to your value, which gives 10001.0000 or 17. If you wanted it rounded to 16.88, you should have used FIXED DECIMAL instead of FIXED BINARY.