bug#50380: Hard to understand NEWS entry about 'save-some-buffers-default-predicate'

[Stefan Kangas]

I find it hard to understand this entry in NEWS:

** New value 'save-some-buffers-root' of 'save-some-buffers-default-predicate'.
It allows to ask about saving only files under the project root
or in subdirectories of the directory that was default during
command invocation.

Could someone who understands it please clarify it?  In particular, it
would benefit from explaining something like "It allows the
'save-some-buffers' command to ask ...".  Also, how is the "project
root" decided?  I think this one very dense sentence should be broken
up into two or even three sentences.