Why mappings are added for wdth?

I have a font with wdth axis from 55 to 100. When converting the glyphs file to ufo + designspace it maps the min from 55 to 62.5 why is this?

from the resulting dspace
```

```
Plase find a test glyhph attached
[wdthTest.glyphs.zip](https://github.com/googlefonts/glyphsLib/files/10179765/wdthTest.glyphs.zip)

Thanks!

Start with the attached wdthTest.glyphs.zip and reproduce the conversion from the Glyphs source to UFO and designspace. Compare the source wdth axis range with the generated designspace mappings, including the 62.5 minimum and map entries, then determine whether the behavior is intentional or should be changed.

Written by the indexing model from the issue text.