Rick,

Rather than thinking about the target travelling further away with the rotation of the earth, think of the target rising or dropping with the earth. The earth rotates from west to east, so if you were shooting towards the east, the target would rotate and drop down a little bit while the bullet is in flight, and the bullet would then strike higher on the target. So you need to dial a little less elevation to bring POI down to POA.

If shooting to the west, the target would rise while the bullet was in flight, and the bullet would strike low on the target. You would be required to dial a little bit extra elevation to bring POI up to POA.

Found this demonstration vid: