The Match job for a base object does not attempt to match every record in the base object against every other record in the base object.
Instead, you specify (in the Schema tool):
how many records the job should match each time it runs.
how many matches are allowed for manual consolidation.
This feature helps to prevent data stewards from being overwhelmed with manual merges for processing. Once this limit is reached, the Match job will not run until the number of matches ready for manual consolidation has been reduced.