Prints from Lightroom Classic are printing too small

I am trying to make a print to fit the dimensions of a mat I have already cut. In Page Setup I set the paper for 13 x 19 Landscape, and set the Cell Size in Print module at 9.3 x 13.32, which is slightly larger than the mat opening. However the finished print measures slightly under 9 x 13. 

I am printing to an Epson ET-8550 printer. I have been printing lots of 7.5” x 10” prints on 8.5 x 11 paper and they come out the exact dimension as expected.