It means any healing you get gets 15% extra, so for example a healing spell from a skill cast on you or by you on yourself will give you 15% more health than it would without RF being up; I'm no expert so don't know if this also boosts healing pots, I would guess it would but don't know.

Not sure what stats you''re referring to, but tooltips for skills certainly don't get updated on-the-fly if a buff is adjusting their effect and I suspect other info likewise may not be updated in real-time for temporary changes like this.