Franz interprets a bouncing spell incorrectly

I cast a custom spell that is called Jumping Jolt. The description of the spell is as follows:

“You release an arc of lighting at a creature within range. Make a ranged spell attack roll against the target. On hit, the target takes 4d12 lightning damage, and you can cause the spell to jump to another target within 20 feet of the first target making a new attack roll for each target. The spell cannot hit the same target twice, or jump to a target out of the spells range. The spell can jump a maximum of five times.”

Now to be fair, it is a little ambiguous how many times the spell can jump if you don't read the very last part. But if you do read it, it's fairly obvious that a maximum of six opponents can be hit. When I cast this spell and clarified that I wanted 3 people to be hit, I did the necessary rolls all at once and told Franz to make the appropriate changes (the spell hit all three targets). Franz then didn't reduce the hp of the third one. He said that “The spell says that it can be made to jump to another target, so you can't make it jump more than once.“

Now I think that it is pretty amazing that Franz is straight up refusing to do something that is strictly against the rules, but unfortunately his interpretation of the rules in this case is wrong.