I know there's some lag time in depositing money in an atm, and actually having access to it. For instance, someone could write and deposit (in a atm) a rubber check for $1000, then request $900 in the next transaction. Of course, you'd be hit with a $30 NSF fee, but what the heck, you just made $900. Banks are smarter than that. That's the reason for the limited withdrawal at atm's. Tellers usually go in the next business day and account for all the transactions.
If you deposit $1000 in an atm on a Saturday afternoon after the bank closes, and charge money that Monday through the same account, assuming the money is in your account, it's very possible the $1000 hasn't been verified yet - depending on the punctuality of the employees at that particular branch.
On the other hand, if you electronically transfer funds form a savings account to a checking account online, those funds should be available right away.
Wells Fargo could easily waive that $30 - depending on how bad they want to keep your business.