they just haven't updated it in awhile, when the price of STEEM was at $3.5 then the 3 STEEM you received would have been worth $10 instead of the $7.36 it says you have.
It should say receive 3 STEEM worth approx $10. The currency is still only months old so yes it will be up and down , it will smooth out with time like all solid currencies do.
RE: I just signed up but did NOT receive $10 worth of Steem Power