Training targets aren't calculating damage correctly

I am using a Soraka with 325 AD who has a 52% armor pen and 10 lethality. I'm attacking a training dummy for 179 per auto.

According to the game, the target has 100 armor. Now, according to the listed damage formulas, the dummy is listed as having 100 armor and should take half damage if I didn't have armor pen. However, without lethality, he should be calculated as having 48/100+48 = 32.4% damage reduction.

I should be doing 67.6% damage with my autos or 219.7 per hit. I'm missing 40 damage per hit or 20% less than I should be doing.