I think what happened is they put through an authorization for the full amount of the tickets, but were unable to issue the tickets right away. They never put through a full charge against those tickets though, so the charge is still pending.

When they actually issued tickets, they put through a charge., but one for each ticket.

The issue is more than likely how long your bank lets an authorization hang out there before they drop it off.

I know something very close to that happened to us last week with a puddle jumper airline in Belize. They charged us for tickets, but charged us the wrong amount at the counter. She immediately voided that transaction in her system, and handed me the void confirmation. She then charged us the correct amount, which was a few dollars less.

However, because that first charge was authorized, but not charged, when it was voided their system just kept it from being charged. But the amount of the ticket was pending on my statement for the week that the bank holds it till they roll it off. There's really no way to reverse an authorization, only a charge, so it has to wait until the bank rolls it off. How long it takes to fall off is up to your bank, usually debit cards are 1 to 5 days, but credit cards can be up to a month.

In most cases you don't see it because the tickets are issued and the charge made right away. In this case because the authorization did not match up with the charge, your bank treated it as four transactions instead of just one.

It will fall off, but there's nothing United can do to make it happen faster, it's all your bank at this point.