First time experienced this, is this normal?

Combimed shipment sent and buyer requested return on one item due to not fitting, ie change of mind, not faulty. No problem with this, and was confirmed before purchase that they could return any item that didn't fit. I have approved this change of mind return. Just noticed the entire payment for the whole shipment is now on hold by paypal, causing me a shortage of funds in my account. 

Is this normal for a hold due to change of mind, and also for full value of invoice not just the value of that one item being returned?