After an arrow hurts an entity, the primary Potion duration is divided by 8 whereas the extra CustomPotionEffects are applied without reducing their duration (though the item lore on a tipped arrow displays the reduced duration correctly)

Either that or the applied duration should be unaffected and the displayed duration is reduced when it shouldn't

Reproduction steps:

• Run /give @s tipped_arrow{CustomPotionEffects:[ {Id:1b,Duration:3600,Amplifier:0b}

  ]}

• When hovering over the item it shows a duration of 22 seconds (3,600 ticks / 20 t/s / 8 = 22.5s)
• When getting hit by the arrow when thrown, the applied duration is of 3 minutes (3,600 ticks / 20t/s = 180s)