The skill rank descriptions don't clearly describe which damage type is getting modified.
Ranks 1-3 of this skill modify the EM damage done by electromagnetic weapons to do 2.0x the damage instead of the 1.1x/1.2x/1.3x increase at rank 1/2/3, respectively as per the skill description.
Rank 4 of this skill only modifies the hull damage done by electromagnetic weapons instead of the EM weapon damage.
Details
Form ID 002C53B2 [PERK]
Game Version
1.7.36.0
Language
English (EN)
New Game
Yes
Reproduction Steps
Examine the skill descriptions in the game, and look at the PERK record in Starfield.esm via xEdit.