Ok, here's what you need to do:

1. Go into the Symbol Manager from the main menu: Symbols -> Symbol Manager
2. At the top, check the box that says "Show fill style symbols" if it isn't checked already.
3. In the symbols listed in the scroll box, find and select the symbol Tile Brown L Fill.
4. Select the Scale button on the right side.
5. Enter a value you want to scale the symbol by in the "Scale selected symbols by:" box (e.g. 2 for twice as big, 10 for ten times as big, 0.5 for half as big)
6. Hit OK, then hit OK again to get out of the Symbol Manager.
7. Save your map.

The draw tool should now draw the floor with the symbol scaled larger or smaller depending on what you chose above. Not that since the symbol definition you just scaled is defined in your existing map, this change will effect the size of the symbol in this map only.

Hope that helps.