Supplemental Secured Property Tax Bill

In March of this year, I moved into a townhome.

I knew that there was a Supplemental Tax bill on its way.

However, received two bills with different owed amounts with the same due dates.

For the first bill, the first and second installment is $622.

Due date for the first is 12/31. Due date for the second is 04/30.

For the second bill, the first and second installment is $950.

Due date for the first is 12/31. Due date for the second is 04/30.

The only difference that appeared (at least to me) to matter was the Roll Year.

For the first bill, the Roll Year is 18-19. For the second bill, the Roll Year is 19-20.

Does the first bill occur because I moved into the townhome in March? March of 2019?

I'm not an expert, here. So go easy on me.

Thanks in advance!