Base recovery rate starts at 10 HP and increases by 1 every tick. With Signet active in a pre-ToAU zone, base recovery rate increases 3 HP per 10 levels over Lv.1, and the amount healed increases by 1 HP per tick for every 300 maximum HP, capping at +5 with 1200 HP.
All increments are cumulative. If you are interrupted while healing (from standing or being damaged) recovery is reset back to base. If you are healing, even at max HP and MP, and your max increases during this time (such as coming out of weakened status), the culmination applies, and you will not start healing at base.
Amount healed = (10+hHP)N + N(N+1)/2 where N is the number of healing ticks. A /healing tick is 10 seconds, but the first tick takes 20 seconds, so be sure to factor that when calculating the number of ticks over time. (For example, if calculating how many ticks there are in 5 minutes, do 5 * 60 / 10 to determine the number of 10 second ticks, then just subtract 1 tick to factor-in the first 20 second tick.)