Just because both books have a style called block_13 does NOT guarantee they are even close to the same unless the book was CREATED with the same stylesheet
A lot of stylesheets (with sequence style numbering) are simply First Use of that style
Calibre# assigned in conversions are that way. A lot of times, similar input, results in similar style names.
It just happens. Don't Borrow a stylesheet from another books conversion (

I do open the other sheet to see what was done for the style I wish to emulate in the book being edited

)