Just to clarify, not that it matters because we all catch your drift -
10 is the personnel. It refers to the number of RBs and TEs on the field. For example, 10 would equate to 1RB,0TEs, 21 being 2RBs,1TE.
The personnel does not indicate the formation, although it can heavily impact what formation may be called. To use your example, you can have a 2x2 or doubles set out of 10 personnel, 11 personnel or anything really. Utilizing multiple personnel groupings within a single formation gives teams flexibility, and allows them to try and find advantages in 1v1 match ups based on alignments.
Because defenses are constantly aware of what personnel grouping is being run onto the field by the offense, they generally match their defenders to how they see best fit to defend that down and distance with those particular players.
the advantage becomes obvious when teams can use different packages, like 12 personnel, to run an extra LB on the field, and then line up or motion in a way that allows that extra LB to be forced into a coverage situation that is not ideal. The same can be said with the run game.
It truly is a chess match.