Btu or sq feet of home

Question

just bought a new home 1654 sq feet the air downstairs is working fine
upstairs is not cooling down much i was wondering how many btu's or sq feet would my unit cover

i have a weather king model # 13aja30a01 13 seer???
also why cant i find any info about this mode or ones that
begin with 10 or 12 in the model #

thanks
madeline