When using NBTExplorer to add custom potion effects for a splash potion, the actual duration is divided by 3/4, yet the tool tip still displays normal duration time.

Example, I made a splash potion to last 20 minutes (24000 ticks), and it only lasts around 15 minutes. However, the tool tip still says it lasts 20 minutes.

My solution, exempt custom potion effects from splash duration calculation and use the custom value directly.