The hipfire FOV stops at 1.642857 (115 HFOV 4:3), it does not go any higher. So if you select another FOV Type than multiplier, this is the maximum. If you are using a higher FOV, you have to enter it as a multiplier, as this is the only way the calculator can both lock the hipfire FOV at the maximum and calculate the ADS and scope FOV above 1.642857.