Video resolution 820x312 won't stick

Is this a program bug?
I’m trying to add a custom video mode of 820x312, but it always changes to 824x312.
I enter the ratio as 205:78 yet Shotcut changes this also to 824x312

Please explain.

Thanks

Interesting silence…

For some reason I forget at the moment - due to a limitation somewhere I care not to take the time to locate again - the width is coerced to be a multiple of 8:

Handbrake to the rescue…