The boxes will almost ALWAYS show max crz altitude for current conditions and figures.
One other small,
very small, caveat: the Max Alt may be off by, ohhh, 100-200 feet if you're heavy and fly into warmer air than was input on the PERF INIT page TOC OAT field while on the ground.
This airplane's FMC doesn't seem to receive updated SATs automatically.
Additionally, the FOB indication increases by tonne or so on departure. It might appear you're "making fuel" initially. My assumption is that this is due to the deck angle. Not sure of the impact on MAX ALT display, but another assumption would be that it would initially lower that output from the pre-takeoff number.