Credit to Limp_Athlete_9982 for pointing this out to me. https://www.reddit.com/r/Wizard101/comments/1jix5ns/2000_storm_damage/
Last I checked, 12 + 4 + 7 + 15 + 10 does not make a number anywhere close to 1624.
I only tested this on my fire, as OP did on Reddit, but it seems that if you take the level 40 scales of knowledge elixir, you get a serious boost to your storm damage. This isn't just a visual bug, it actually does give you the advertised damage (although capped at 247%).