Change your preferences here.
Inflicts intensifying poison on the target that does 1/16 max HP damage the first turn, 2/16 max HP on the second turn, then 3/16, etc., adding 1/16 to the damage each turn. Reverts to normal poison if the inflicted Pokémon switches or if the move Haze is used. If a Pokémon used the move Rest to recover from Toxic and it becomes poisoned again by Toxic, then the inflicting damage count does not reset. It continues from where it left off of. So, if last time Toxic removed 3/16th of your HP, it would remove 1/4th of your HP.
Toxic is not very good in RBY. First of all, both sleep and paralysis are more valuable statuses. Besides that, Toxic's poison turns into normal poison after a switch out, so it's basically a useless move that will deal less damage than burn or normal poison unless the Pokemon stays on the field for three turns or more.