If you run a command like:

/give @s minecraft:lingering_potion{CustomPotionEffects:[{Id:19b,Amplifier:0b,Duration:80}]} 1

The potion duration listed on the potion is stated as 1 second (20 ticks), rather than the inputted 4 seconds (80 ticks). The actual potion effect time is correct, however. I've tested this for a few different potion effects, and it always seems to be the case no matter which effects the potion has.