This comes from the fields editor
I believe that the : should be aligned, for ease of reading. So when there is between 10 and 99 fields, the first field should start with 01: (and so if there is at least 100 fields)
Or better, I’d prefer that the numbers were outside of the field, so that I could just type “st” and go to “style”; while now I have to type 13, which is less intuitive. (But this require more changes to the code, so I’d understand if only the first one would be done)
The numbers are only there to facilitate the Reposition button. Since drag&drop is supported these days, the Reposition button could be removed and the numbers with it.
If I can offer my opinion - I wouldn’t remove the reposition button, because it might not be clear to users that drag and drop is supported. And I don’t think the numbers not being aligned is a big problem, to be honest, this seems like a very minor detail to me.
I didn’t know, for example 
Altough removing the numbers would make it more clear that drag and drop is supported, I also vote to keep the Reposition button for a different reason: it is very cumbersome to drag fields around when you got so many that they cause overflow.
But @ArthurMilchior, the fields dialog will be ported to Svelte anyway. It will be a lot easier to align the numbers with web components.