You could use a set of filters like these to match all the numbers from 1440 to
2878:

"+*/14[4-9][0-9].png"     match 1400 thru 1499
"+*/1[5-9][0-9][0-9].png" match 1500 thru 1999
"+*/2[0-7][0-9][0-9].png" match 2000 thru 2799
"+*/28[0-6][0-9].png"     match 2800 thru 2869
"+*/287[0-8].png"         match 2870 thru 2878

This trick relies on the character range syntax.

See the filter syntax documentation. <http://www.httrack.com/html/filters.html>