There are multiple problems when it comes to number input e.g. there is empty input ref value when inputted value is not a number. So, in the context you will have null but on UI you'll still see value with overlaying label.
For more limitations you can read following article.
https://technology.blog.gov.uk/2020/02/24/why-the-gov-uk-design-system-team-changed-the-input-type-for-numbers/

when inserting incorrect number value the input state is set to null.
However, input ref still has incorrect value and causes input label to overlay value which is still shown.