As we all know when we tear off tamper proof label, the hidden tamper evident words will come out. Positive and Negative dosen't mean the revealing words is good or bad. It means the version of it. 

                    Negative means that when we tear it off, the words 'VOID' will be remained on the sticker, and the rest part revealed on the surface where we stick to. (as the picture shows)

                    Positive means that when we tear it off, the words 'VOID' will be revealed on the surface where we stick to, and the rest part remained on the sticker. (as the picture shows)

                    Both of them are good with revealing effect, and also can achieve tamper evident function. Just the version is different, so we can choose the one we like better.