That is the spell ID. Fifth argument of the event, correct?
http://www.wowhead.com/spell=116/frostbolt
http://www.wowhead.com/spell=228597/frostbolt
Looks like the game is confused and thinks you’re casting two spells at the same time. I don’t know the difference, so only check for one of them. In your code, just use a line like “if ID=116 then return end” and the code will ignore that spellcast.