MacBook Air missing 130gb

Sounds to me that you've received a MacBook Air with only a 128 gb SSD. As Neuroatonomist suggested look for the invoice of your Mac. It should list the amount of storage your Mac should have.

My 2017 MacBook Air did come with a 256 gb SSD. As was mentioned on the specification/invoice. It was also more expensive compared to the default model. Hardware wise the same, just the only difference being the size of the build in SSD.

As mentioned by @neuroanatomist - sorry to say there was a wrong assumption of having a 256 GB SSD. Judging from the usage categories in screen shot a decision of what to keep and what to remove is required if wanting to upgrade to Big Sur.

It appears you received a 128 GB MacBook Air. Check your purchase documentation (order/receipt).

The base option for that model was 128 GB.

Can you post a screen shot via Apple Icon on desktop >> About this Mac >> Storage ?