Firmware versions 5.0.0 and higher support firing down to 1/100th of a second; 4.0.0 and lower is limited to 1/10th of a second firing resolution.
18M Hardware A does not support 1/100th of a second timing and will round to the nearest 1/10th second. Any hardware purchased after June of 2015 supports 1/100th of a second timing. For more information on determining your hardware version, see Hardware Hammered Out.