I am sure that I should have a positive balance on my wallet but I am seeing a negative, why is that?

The wallet balance is updated several times a day, as it is linked to all activity you have on xChange. Possible reasons for the balance to suddenly turn negative can be, but not limited to: you just purchased containers (the purchase price is automatically registered in the wallet upon acceptance); you just reported picked up containers in leasing, for which you pay pickup fees. If you still have further doubts concerning your wallet balance you can email payments@container-xchange.com for further clarification.