I put $ 60 in the Bitcoin ATM to convert the $ 60 into bitcoin but only half of my money is in my wallet
Bitcoin ATMs charge fees for the currency exchange. Sometimes they use amazing differentials in exchange rates. They are usually very expensive. Possibly more for small amounts. Check your receipt.
If you think the machine made an error, contact the operator (do not contact the owner of the floor space, since most of them only rent the floor space they do not own the machine).
and 4 days have passed
Waiting longer will not cause more BTC to appear. The transaction is made.
Footnote / digression:
Bitcoin ATMs are not automated teller machines (ATMs), they are automated currency exchanges, something different. Calling them BTM is a little better.