So the issue here is that the engine is not being consistent with the variable unit.
Initially you have 50000 cm/s.
When you type 500, the engine remembers you were in cm/s, but chooses to display it as m/s, so you end up with 5 m/s which is the same as 500 cm/s. You have the right value but not displayed in the original unit, so that’s confusing.
Then you type 500 again, the engine remembers that you are now in m/s, since it’s the new unit it choosed, so now you end up with 500 m/s which is 50000 cm/s.
When you compile the engine realise it shouldn’t have ever switched to m/s so it converts the value back to 50000 cm/s (same as 500 m/s), so the value didn’t change in reality.
I think that’s a bug that should be raised to Epic, basically the issue is that the engine switches to m/s after the first edit and only goes back to the proper unit after compile. It should always display as cm/s in that case, otherwise you get the issue that you have where inputing 500 twice will lead to two different value.
Hope that makes sense. You can report the issue here: https://unrealbugsubmissions.epicgames.com/s/?language=en_US&token=J3ikc3nt9y1pvlaRrT4z9iOvdylQdS967McJ
Feel free to link this thread and my message if you think it makes sense. You should include your video which displays the issue quite well.