Small point here, but fractions pretty much always round down in Pathfinder, so it'd be healing of 1 hp.
"Unless otherwise noted, whenever you are must round a number, always round down." <-- Core Rulebook, Getting Started.
ThatHealer, the spell never references "total damage across all creatures affected". As pointed out, that would include objects too if you think about it. It's extremely clear what the spell intended, as all the responses here indicate. You shoot off a fireball. You roll 40 damage on 10d6. You deal 30 with the fireball, and heal 10. Anyone in the fireball's area then rolls to save for half (15 damage) or takes the full (30 damage) plus and minus all resistances/vulnerabilities/etc.
This is not a difficult thing to understand.
Opp thanks for reminding me Karui