$ seq 1 100 >seq.txt
$ less -M seq.txt

Status line says:
"seq.txt lines 1-23/100 21%"
Press 'q'

$ busybox less -M seq.txt

Status line says:
"seq.txt lines 1-23/24 96%"
                    ^^ ^^^ (Not 100 lines)
Press 'q'

$ seq 1 100 | less -M

"lines 1-23"
Press '>' and then press '<':
"lines 1-23/100 21%"
Press 'q'

$ seq 1 100 | busybox less -M

"standard input lines 1-23/24 96%"
                           ^^ ^^^
The total number of lines and percentage shouldn't be shown if stdin wasn't
finished reading (i.e. no EOF encountered yet).
Press '>' and then press '<':
"standard input lines 1-23/101 23%"
                           ^^^
('vi' and GNU 'less' say 100. I'm not complaining about this off-by-one, but it
could be a separate bug report.)