At the end of January 2013, the balance of office supplies is P2,000. In February, P2,000 worth of office supplies was bought. At the end of February, it was discovered that supplies inventory is P5,000. What is the adjusting entry?

+ p1,000?

Are your amounts correct, because it looks like they are wrong. You have an ending Jan balance of 2,000 of supplies on hand plus 2,000 worth of purchases in Feb equals a 4,000 ending Feb balance, but you have an actual inventory amount of 5,000

If this is a homework problem I would double check your amounts. As I have never seen this type of situation. Usually you will always have more account balance, than the actual physical count balance. Also I would double check your transactions for the month for other purchases. Or you could have missed recording a purchase.