We create a key from the first sequence of arabic numerals in the 300 $a; pagination enclosed in square brackets is discarded. By default, two numbers within /- 5 will match, unless the record is non-print (ie. cassettes, videorecordings), or the volume designation is given (eg.2 v.), in which case the two numbers must be exactly the same.

A missing 300$a in either record does not fail the match.

Note

The software does not rely upon the 300 $a for the SMD; instead, this element is extracted from the 007.

The following note is found on the XMTYP (007) crosscheck page:

... if both records lack an 007, then subfields $a, $b, and $c from 
the 300 field in each record will be extracted, normalized, and compared 
(as a single string). If this comparison fails, then this crosscheck fails.

Thus, it's somewhat important that XMTYP always be configured in the match rules.