need help about compressing map size

[Firesparker]

I did some research and a lot of people said that if the map size is too big, use the flush function on the operation tab to compress the size. I did it, but the map size still say its too big to be hosted. I don't know what else I should do.

If someone knows the solution to this, please tell me how you did it so I don't run into this problem again. Thanks.