That is normal: It is the size of the image in memory and includes all the undo 'saves' and any additional layers, channels, etc.
Example: I start off with a file on disk - a Gimp .xcf with a path. size 15,874 KB
Open in Gimp before any editing 3.4 MB in memory. I duplicate the path for splitting, now 3.6 MB. Do all the selecting applying path edits on both paths size now 11 MB.
...but when I come to save it back to disk the file size is 16,876 KB. Small increase due to the extra duplicated path.
There is a setting in Edit -> Preferences -> System Resources for undo levels, default is 5 You could maybe reduce that, might make a difference (not too sure it does) There is also a dock Windows -> Dockable Dialogues -> Undo History does what it says, will reduce that size in memory.
Example: I start off with a file on disk - a Gimp .xcf with a path. size 15,874 KB
Open in Gimp before any editing 3.4 MB in memory. I duplicate the path for splitting, now 3.6 MB. Do all the selecting applying path edits on both paths size now 11 MB.
...but when I come to save it back to disk the file size is 16,876 KB. Small increase due to the extra duplicated path.
There is a setting in Edit -> Preferences -> System Resources for undo levels, default is 5 You could maybe reduce that, might make a difference (not too sure it does) There is also a dock Windows -> Dockable Dialogues -> Undo History does what it says, will reduce that size in memory.