Spellscale Kobold Question

[mastratton]

I don't know if this is a bug, or if I am just misunderstanding the rule.

I have a kobold oracle, and he has the Spellscale Kobold ancestry feat.

The feat says:
"A trace of draconic magic flows through your veins. Choose one cantrip from the arcane spell list (Core Rulebook 307). You can Cast this Spell as an arcane innate spell at will. A cantrip is heightened to a spell level equal to half your level rounded up. You gain the trained proficiency rank in arcane spell attack rolls and spell DCs, and your key spellcasting ability is Charisma."

Now, as a 2nd level oracle with this feat, I gain Trained proficiency (+4) in arcane spell attack rolls and spell DCs, and my key spellcasting ability is Charism (+4 bonus). So, shouldn't that make my attack roll with this cantrip +8, and my spell DC 18? Because HLO shows it is +4 and 14, respectively.

Is that an error or am I misunderstanding this feat?