What does AssignedMemory in Storm UI mean?

I have a topology running in one machine with 3 worker nodes. In the storm UI, Worker Summary shows some number in "AssignedMemory" column. What does that mean? I observed that it has a linear relationship with the no. of executors. i.e it is always 128 times the no. of executors. What am I missing?

storm.yaml

supervisor.slots.ports:
    - 6700
    - 6701
    - 6702
supervisor.childopts: " -Xms512m -Xmx1024m  -ea"
worker.childopts: " -Xms1024m -Xmx2048m -Xlog:gc:artifacts/gc.log -ea" 

Attached screenshot for reference.

PS: I understand that running one topology in more than one worker in one machine doesn't make any difference. I am just experimenting.