Owlinus doubles the damage from spells

I played in standard and owlinus’ swipe dealt 10 damage to my face. it seems like it added spell dmg and then doubled the damage of the entire spell, while its effect says only the spell damage is doubled (so +1 should be +2, +2 should be +4 and so forth). Is that how this card supposed to work? it adds spell damage then double the entire damage? ‘Your spells get double bonus from Spell Damage .’

They probably had a dragon or location on the board also giving spell damage

They didn’t, it just doubles the damage, that’s a bug - it should only double the spell dmg bonus