We've been getting similar charges lately when a single payment for multiple charges is made.

The initial payment for the full amount sits in "pending" for a few days (we assume it's just a hold for that amount rather than a payment), and is then reversed.

The actual individual payments are the only ones fully processed.

It's a bit annoying as it holds extra funds for a short time, but it's OK for us.  It may be more of a problem for people buying higher value items than we do, though.