First of all, you can see January, February, March.....December indicates your rent collection amount. and Accrued/green color column reflects your unearned rent/accrued rent.
Lets see cell no C19 & D20, It reflects the total sum of collected money and uncollected money accordingly.
Suppose, Ashiq Cell no C9 monthly pay the rent to me about 3500 tk. As you can see in cell no D9 is 0 because there is no accrued is available. On the other hand, in the month of February, as you can see Ashiq pays 3200 tk. So, accrued amount is 300. It also plus with next month accrued payment. (cell no J9). If any person don't give then it will automatically show you the total accrued in every month.
Suppose, Rifat pays 1550 tk. in every month. Cell no C11, Mr. Rifat didn't pay any money in the month of January. So, the accrued amount is 1550. But he paid in the month of February, He paid 3000 tk. so the accrued amount is 100tk.