Pended numbers represent the number of listings that went into the "pending" status in that month. For example, if there are 100 pended listings in January, it means that 100 listings had their status changed to "Pending" in January.
What is Months of Inventory? The "Months of Inventory" measures how long it would take to sell through the current, active inventory in the market place, at the current pace of sales, if no other listings came on the market as of right now.
For instance, if there are 1,000 active listings and 100 of them sold in a given month, the Months of Inventory would be 10. It would take 10 months to sell through the current, active inventory in that month at the current pace of sales.