Many people have had this problem
Threads about this:
https://www.warzone.com/Forum/269656-map-preview-size-gamehttps://www.warzone.com/Forum/259015-another-problem?Offset=0https://www.warzone.com/Forum/273616-map-upload-problem-appears-small-top-leftI think this may be a problem with your viewbox. Under document properties there may be a viewbox setting under "scale". If so, make viewbox x and viewbox y 0.
If not, this is a more complicated issue to fix.
Try going to your xml files (control+shift+x) and click on the top thing which should be your svg id.
Then in the box on the right called "name", scoll down to viewbox. Change the first 2 numbers to 0 and 0, and change the 3rd / 4th numbers to your width / height.
This should fix the problem you are experiencing.
Edit: This is what your viewbox should look like:
https://postimg.org/image/6n3lfg2uf/
Edited 11/26/2017 23:27:36