The allowance for the marketing carrier of the first segment will apply to the entire itinerary. Thus, when you check in at MAA, you should receive the same allowance as you received when you checked in at SFO.

*A handles this pretty well and the agent at MAA should see on screen what you see on your e-ticket receipt. But, if he doesn't, it is always smart to have a hard copy of your e-ticket receipt (the one which actually shows e-ticket #'s) as that shows your baggage allowance.

Once in a blue moon, you hit the poorly-trained outstation agent and are stuck. In that case, my advice is to pay whatever the bag fees are with a CC, request a refund -- in this case from LH -- after your return and then initiate a dispute on the CC and file an online webform complaint with DOT. But, this latter tactic is becoming less & less necessary.