[Inkscape-translator] Trouble with terminology: source width/height, etc

Hi, I'm having trouble translating some strings from /src/ui/dialog/filedialog.cpp

Source left bound Source top bound Source right bound Source bottom bound Source width Source height

What is the "source" we're talking about here? Is it the SVG source code? And why is it bound somewhere?

Any advice in the tight direction will be appreciated, thanks.