You can restrict the maximum number of lines returned in the Configuration->Display Settings->Max displayed lines per file. If you set it to 15 it will only record the first 15 lines found.
If you hit that limit FileLocator Pro will display an "...additional lines truncated..." message.
The default value is 10,000 lines but when searching a large group of files with potentially a large number of hits this can cause memory issues. Another memory related setting to keep in mind is the Character Processing->Maximum characters per line value:
This defaults to 20,480 characters, which is normally fine with text based formats since few files have lines that long. But when searching binary formats, such as EXE and DLL files (which may not have EOL identifiers), this can result in very large result sets.