I have read the documentation. But I don't understand it. I am a "involuntary DBA". And I have a hard time following most Microsoft documentation. I tend to look for forum or blog postings that translate it into a "For Dummies" version.
In my research, looking for an explanation I can follow, I came across this from Paul S. Randal, who has some legit credentials for his expertise.
https://www.sqlskills.com/blogs/paul/inside-sys-dm_db_index_physical_stats/
In here he says,
"
The DETAILED mode does two things:
"
So, then why would the fragmentation calculations be different between LIMITED and DETAILED? If you look at the fields I'm pulling, fragmentation is all I'm looking at.