As from version 2.0 the search relevance customization is possible.
The values on the search relevance otpions page are only valid for non-fulltext searching. Fulltext lookup has a built in relevance.
The plugin defines relevance values from scale 1-10, 1 being the lowest and 10 being the highest value. You can define a relevance value for each field where the plugin looks.
The relevance is calculated based on these values with a simple formula.
The formula is:
[field 1 relevance value] x [phrase occurence in field 1] + [field 2 relevance value] x [phrase occurence in field 2] + ...
So if the title weight is 9 and the phrase "test" was found in title twice, then the title relevance is: 9 x 2 = 18
The same calculation is made for each field with the corresponding relevance value. In the and these values are summed. This sum is the result relevance.
Exact match vs. Non-exact match relevance
Exact match relevance is calculated without examining each word in the phrase, only checking the exact phrase for occurences. Non-exact match relevance is the opposite, where each word is checked separately.