Hi Robyn,
Welcome to the Apple community where some of us try to do our best to help each other
I'm no expert, but there is something you might want to try:
Sometimes the deleted files do not show up, because they are still in the trash, and still count.
Even when the trash is emptied, they may not register ... until you "Restart".
Apple has a support page that may be useful to you:
How to free up storage space on your Mac:
https://support.apple.com/en-us/HT206996
If none of the above helps you reach a satisfactory position:
Please feel free to post again, preferably giving details of which year MacBook Air ,
and which operating system you have installed on it.
(Might need to cllick the Apple icon on the left, in the top menu bar, select "About this Mac" for the info.)
That might help someone give you more specific, or expert, help. if needed.
Cheers