Thats an adjustable chip. You can vary the timing with the different settings..word of caution: untill you learn what timing the different settings will apply to your engine keep your foot out of it. If you don't have enough octane to satisfy high timing, head gaskets and even more serious engine damage can result. Detonation from lack of octane can fry pistons, beat the bearings to death and other things. Go to Caspers site and you may get info there or better yet maybe he will respond here or to an e mail. Names John and he's a super nice guy.