Mine's the Third edition, Eleventh Printing with a copyright date of 3/2002.
I looked it up, and it turns out I was off--they list 23.4 grains for the max, not 23.2:
Lyman 429421
23.4 grains of 2400
1232 fps
36000 cup
I see that you were looking at the data for the Thompson bullet, 429244.
Lyman's Cast Bullet Manual may not be the best example. The data in it is quite old, dating from 1980. I'll admit that one advantage to that though is that it includes data for older powders that it's tough to find data for.