by default all NPC spells will be interrupted. The whitelist is for players unless you edit "KickBot.lua" and change "AllowAnyNPCSpellInterrupt = 1" to "AllowAnyNPCSpellInterrupt = 0"
Cast bar 0.5 will only work if you have small latency and no global cooldown to block the casting of the interrupt spell. The 1.5 second was put there so you will not blame the bot for not working just because you casted something else that triggered global cooldown
Please read the readme.txt how to do the full setup. In those small boxes you need to put the keybind that will cast the macro to interrupt. If you DPS the "big add" as main target than your macro is probably :
/stopcasting
/cast Counterspell
- If you DPS boss and have the "big add" as focus target, than your macro would be
/stopcasting
/cast [target=focus] Counterspell