There is a fabric calculator on the items page, on the left and below the image. It says:

Calculation Results:
Fabric Size: 20" x 17" when stitched on 16ct Aida
We recommend at least 2 inches of extra fabric around the design for framing and finishing.A piece of 20"x17" fabric will give you 2.4" of extra fabric on the left and right, and 2.05" on the top and bottom.

Note:The stitched area will be 15.2" x 12.9".

On 16 count, the design size would be 15.25 x 12.9. Please don't forget to add 3" per side for framing, so you would need a piece of fabric 21 1/4" x 18.9"

To figure out how to calculate a change in size, take the stitch count of your design, in this case 244 x 207, & divide each by the fabric count you are considering, in this case 16 count. You will end up with the finished design size.
244÷16=15.25
207÷16=12.9

There are also fabric calculators that you put in the stitch count, & the fabric count, & it will figure it out for you ( one on this site) but I have done it this way for so many years, it just comes naturally