Phanx's way is probably better but...
Code:
local text = lib.gen_fontstring(f.Health, cfg.font, 18, "OUTLINE")
text:SetPoint("RIGHT", s.arrow, "LEFT", 6, -8)
s:SetScript("OnValueChanged", function(self, value)
text:SetFormattedText("%d", value, 0)
text:SetJustifyH("RIGHT")
end)