The fabric sent to you is the cut size that you will need to stitch this, plus a 3 inch margin, which assists the framer to stretch and frame this correctly. The stitch count is 300 x 298. To get the right size, just divide this stitch count by the fabric count and add 6 inches to both the width and height of your answer.
300 x298 ÷ 14 = 21.4" x 21.3" , but add 6 inches and it = 27.4" x 27.3".
300 x 298 ÷ 16 = 27.4" x 27.3", add 6" = 27.4 x 27.3
300 x 298 ÷ 18 = 16. 7 x 16.6, add 6" = 22.7" x 23"

The higher the fabric count, the smaller the size, but the picture comes out the same, just smaller. ECS will allow exchanges of fabric if you do NOT cut it or send it back without the label/plastic wrapping, if it had same.
I am not an employee of ECS, just a stitcher in this chat group. Please feel free to join us.

This is the size for 36 X 51 with the order for framing for 14 c If you want to make it in a smaller version which is 18 or 16 c you still can do it. But it will come smaller as a picture. Have fun

Su, I got a different measurement on the 16 ct.

300 ÷ 16 = 18.75 + 6" = 24.75
298 ÷16 = 18.6 + 6" = 24.6

Probably a typo....😊

VCESS is right. It must be my brain. Had a horrid day.

Sorry, you had a bad day, Su...was it your foot and back? I'm up with achey legs...drank some tonic water and now I'm awake...for a bit. ☺

VCESS...
Not my foot or my back! That pain is constant. Nope, it was DH! He has to drive if I want to go anywhere. Went to Staples. He got very frustrated about me making working copies of a few patterns. He loudly complained about the cost, the way the new Xerox machine worked and how I made him make mistakes. We got home and he went to the neighbors who will always make him a cocktail or two. I eventually got fed up and yelled back, which solves nothing, but it does let him know how embarassed I was at Staples. Fed up. Really.