I can't quite remember, but I think it actually heals you immediately for that much (2500), and then you get additional regen after that, which would be the 900, for a total of 3400. --- Welcome to GameFAQS, where sharing an opinion is a declaration of war. Resurrect the saint from within the wretch.
Keep in mind that Healing Spring lingers for that 15 seconds. If an ally were to stand in it for the full duration, they would get the 2K regen healing it talks about. Otherwise, they get a minor regen buff for simply passing through.