Found this by comparing hull mod with shield mod on my T3 Federation Frigate. Current max shield without mod is 8014Units. Mod adds 25% additional shield power. Calculated shield is now 10017.5 Units. Displayed in hangar and shown in battle 9959 Units. Units Missing: 58.5. Seems less but try it out with diffrent ships…

Tested it with my T2-2’s from Jericho Techs and lets have a look at how much is missing.

Int: 3874 base with mod 4484 in hangar. Calculated: 4842.5 // Missing:358.5!!!

Fighter: 7193 base with mod8353 in hangar. Calculated: 8991.25//Missing: 638.25!!!

Frig: 11690 base with mod 13575 in hangar Calculated 14612.5 // Missing:1037.5!!!

Thats quite a lot isnt it? In that case i would also check the calculation for hull mods here. This bug in the calculation could also affect them.