How are you checking the size of the edited version? And what kind of image file are you exporting?
If you just drag the photo from Photos to the Desktop, you will get a preview of the edited version, but cannot control the quality and resolution.
To save the edited version at a high quality, use "File > Export > ... Photos" and select Original size and a high quality.
- If you export the photo as a TIFF, you will get the highest possible quality and gigantic file size.
- If you export as a JPEG, select as least "High Quality". Exporting at the "Maximum Quality" might result in a larger file size as the original, which would be wasteful.
