I recieved a 24 hour writ of possession eviction notice when do I have to be out?

You have 24 hours to vacate once noticed is served by the sheriff and it is placed on the premise (Fla. Stat. 83.62). www.krrlaw.com

24 Hours, the Sheriff will come by tomorrow and make sure you leave.

If you are not sure you should call the sheriff's office to be sure. I called the Orange County Sheriff's office for the same question in the Orlando area and found that they do not count the day the notice is posted and will generally provide the following full business day then return to remove you on the day after that. They do not remove tenants on Saturday, Sunday or legal holidays. I do not know the procedure in Bradenton so call your County Sheriff's Office and speak to someone in the Civil Process section. They should be able to give you a good idea.