Custom Framerate issue

So I use Toon Boom Animate 3 for my work. I was supposed to export each of my shots for a project I’m doing at 23.976 FPS which I did, by putting that in as the custom framerate on the export settings as it wasn’t one of the preexisting options. When I handed them over to my director, he told me they show up on his screen as 24 fps. I double checked and I DID export them properly, and when i look at the files in the properties section of my computer the frame rate is just blank. i checked the file on my other computer and it shows up as 24 there too. I checked files for work I’ve done previously where THEY were done in 24 fps and they show up with the proper frame rate just fine. Is it common for files with custom framerates to appear as either blank or some other rate? the only files with proper frame rate my director got were the ones that I edited previously in premiere.