If you’ve just retrofitted your Lightweight Armor to Rank 1, you may be wondering why the Evade Bonus of the E class armors is increasing to 7.7% when you were expecting it to increase to 10.5%. After all, the Retrofit Lab says 0.0% -> 3.0%.
The bonuses from the Retrofit Lab on armor and other percentage-based components aren't additions to the base bonus of that armor, they are a modification to that bonus. In other words, the 3.0% you see above is the percentage by which the D4-E’s base Evade Bonus of 7.5% will be modified. Because there are different base stats within some of the armor groups, it’s not practical to display what the resultant stat will be.
For example, the base Evade Bonus of the D4-E is 7.5%. The 3.0% bonus from R1 of the Lightweight Armor type is a 3.0% bonus of that 7.5%, or an addition of .2% (after rounding). That then modifies the Evade Bonus of the armor by that amount, to 7.7%.
At Rank 5, the 12.2% bonus to that base stat of 7.5% is an addition of 0.9% (after rounding again), adding that 0.9% takes that stat to 8.4% 
This 8.4% bonus is then what gets applied to your various ship builds when you use this armor class.