I can tell you what that means for a human (as I am hypothyroid). Normal low would be toward the upper end of the 4.0 (opposite of what you think). Hypo is above the 4.0 range, hyper is below the 1.0 range for dogs - I think it is more like .4 for humans). Someone who is hyperthyroid can have trouble keeping weight on…someone who is hypothyroid can have trouble taking weight off (it is kind of a simplistic explanation as much more than just weight is affected...actually that is usually the least of the problem).
I would think 1.92 being smack dab in the middle would be pretty good. An endocrinologist usually doesn't want someone (so I'd guess the same for dogs) to be near the 4.0 range because if something changes then you are hypothroid again...likewise they don't want you too low or you could go hyperthyroid (heart issues, etc., can happen if you are hyper). They like to try to keep you in the middle/higher (1.0 - 2.0) end of the range if you are hypo. However, that said, each individual (and I would guess it could be the same for dogs) can react differently and need to be geared toward a different end of the scale (higher or lower). For example, for me...I need to be kept right at the high end (right near .4).
I'm sure if I'm wrong about how it works for dogs, someone will chime in...