Making a video 0.5 sec shorter is not working with speed/duration

[Melissa2851780837cm]

Hi everyone,

Hopefully someone can help me. I was editing a video of 23 sec. However, I also need other versions of that video where I cut the last 0.5 sec from the end every time. (So I need videos from 00:00:23:00, 00:00:22:30, 00:00:22:00 etc). However when I try to shorten the duration of the video with speed/duration it would not let me select any number after 22:24, then it jumps to 23:00. For all other time stamps it works fine, but I am not able to pause or shorten the video on 22:30. Does anyone know how to solve this?

Thank you in advance,

Melissa