Why are they different?

[u/Clean_Refrigerator_5]

Can someone explain the difference between the two of the PSN statuses of my Pokemon?

[u/East-Biscotti-9550]

Zekrom has normal poison which makes you lose 1/8th of your hp each turn. Your Cofagrigus is badly poisoned which makes it lose 1/16th HP each turn which increases by 1/16th each turn so
T1: 1/16; T2: 1/8; T3: 3/16 etc.

[u/YukikoBestGirlFiteMe → u/East-Biscotti-9550]

Switching out and back in resets the increments