You can try:
\d+ - (\d+) of \1
And replace with $1, as group 1 took.
\d , + . (…) , \1 , . , :
num1 - num2 of num2
| |
\________/ must match
, :
\d+\s+-\s+(\d+)\s+of\s+\1
, , , \s+, , . , ..
, , \d+ \1.
\d+\s+-\s+\d+\s+of\s+(\d+)
"1 - 20 of 149", . , , (149 ), $1.
3 , :
(\d+)\s+-\s+(\d+)\s+of\s+(\d+)
\___/ \___/ \___/
1 2 3
1, 2 3.