Technically, you sent sMerits (rather than Merits). As said, they are not reversible unless you’ve got at least 51% of Admin hash, so it’s good riddance to the exceeding 10 you did not want to send over.

A similar thing happened to me not long ago. Whilst being doubtful between sending either 1 sMerit or 2 sMerits, I ended up committing a 21 sMerit TX. Since I tend to remerit post I’ve previously merited before, I have to add an exception so as not to remerit the post again with an additional 21 sMerit TX.