Here is the help article, expand the section for how to report partial rollover:

https://accountants.intuit.com/support/en-us/help-article/form-1099-r/entering-form-1099-r-proseries...

"when 1099-R doesnt state this"

Because the issuer of the 1099-R is reporting for money Out. They don't necessarily know what happened next. That's why you get form 5498, statements, and confirm for yourself what was done next. You want to see the rollover meets the requirements, and that this was not put into regular savings, treated as a contribution for the tax year, did they make up the difference (you already know this is a partial distribution), etc.