@haoxin I'll explain by example as I understood it. Say an enemy cats a spell and it takes 5s for the incantation (starting the casting until the spell actually manifests), and you use interruption, the spell fizzles.
If you use an attack with delay, the incantation now e.g. takes 7s instead of 5s. if you attack again, it takes (in total) 9s. In addition to the casting taking longer, the enemy can't move, so basically you can lock the enemies movement. if you now can apply more delay than time passes (e.g. you can add a 5s delay every 3s), you effectively paralyzed that enemy.
hth