Is this method and math sound?

I assume that I should adjust my OG for the gravity points contributed from the starter. FG of the entire batch from that adjusted OG should give me an accurate ABV. Correct?

OG before starter = 1.121

Volume before starter = 4.6 gal

Starter OG = 1.037

Starter Volume = 0.375 gal (does not include volume of slurry)

So....

(1.121 - 1) * 1000 * 4.6 = 556.6 gravity points*gallon from wort

(1.037 - 1) * 1000 * 0.375 = 13.9 gravity points*gallon from starter

556.6 + 13.9 = 570.5 total gravity points*gallon

4.6 + 0.375 = total gallons of volume

1 + ((570.5/4.975) / 1000) = 1.115 adjusted OG

If my FG = 1.025, than I calculate...

11.75% AVB from adjusted OG, as opposed to

12.6% ABV without adjusting for the starter.

Is this an accurate way to adjust ABV for a big starter?