Searing Bond of Detonation - incorrect detonation behavior

In my particular scenario, I have currently a maximum number of 18 summoned totems.

When at 16 totems, the next cast (supported by multiple totem, so it spawns 2 at once) instead of increasing the number to 18 and exploding, it detonates the 16, spawns 2 extra, and detonates them shortly afterwards.

Does not seem like the correct behavior and it may have potential impact of not counting the 2 extra totems for the total detonation multiplier from the gem and quality.

Please investigate.