Ever have coolant settle after a fill
 

WP/Tstat job. filled back up, bled, etc.
I cannot recall ever where I've top it off....but 2 weeks later, with very minimal driving, I needed to top off 24oz.

Going to monitor and observe. No telltale clues on leaking, pressurized it, did not see the dial drop....

Any system that requires bleeding I give it a free pass for one "burp".

If it needs topping off again worry. If it needs topping off after that find whats happening to the coolant.

I've had this happen too - and my thoughts were the same as stated by Crowz - a stray air pocket must have worked it's way out.

I second. Or third rather. :D

A top up (or two of less fluid than the first) is not uncommon after running for awhile. I'll usually top up a couple times after servicing a cooling system component that caused a loss of significant fluid.