This chart appears on the Rent Roll Dashboard. Loss to lease/gain to lease for a particular unit is calculated as the difference in market rent and in-place rent. The Loss to Lease Burn-off chart factors in the expiration date of each unit and "burns off" that loss/gain to lease after the expiration date has passed. So if a unit has market rent of $1,100, in-place rent of $1,000, and an expiration date of 7/31/17, the loss to lease in August will be $100 less than the Loss to Lease in July in that chart.