. At my company your questions most likely answer is that AERO data calculated the max allowed take off weight based on the current conditions you input into the program for your planned take off. Reference your Performance data section of your Aircraft Operating Manual. You can change the inputs into AERO data to increase your allowed max take off weight ie: use max thrust, change flap setting, change runway.
ACARS is a communication and data link system. At my company it does not do performance data or weight and balance problems.
We use AERO data which is a performance data program for dispatch in which we receive the information over the ACARS. AERO data program is also used for actual landing performance data while airborne.
AERO data takes MEL performance limitations and applies them to your landing data solution. For both dispatch and actual landing performance calculations