then there are few things you might want to do.
check your system units and set them as you're comfortable with, let's say cm.
check your display units and set them accordingly, let's say cm.
go to the maxwell tab and under system set your conversion scale, if you have your units in cm then it should look like this: 100 units in max are equal to 1 mt in maxwell: scene scale 0,01 (0,001 if you set your units in mm and so on).
then check that your model is correct, i mean if a wall is 10 mt wide, it must be 10 mt wide for real.
following these steps you'll get a correct scale.