How long should you keep salicylic acid on for?

Ive got a couple warts on my hand, I bought some Compound W (salicylic acid) to help alleviate them but I can't find anywhere (bottle, box, internet) how long to leave the stuff on. It says twice a day for up to 12 weeks, but doesn't explain when to peel the stuff off. All I see are articles about how too long can irritate the skin and I'm not sure what to do