What is the meaning of scores when comparing reaction classes in the KEGG database

With respect to related R class in KEGG website:  

<http://www.genome.jp/tools-bin/relclass?RC00064>   
  
 What is the biological or statistical relevance of the score? How is it computed? And does it signify the bonding strength of how probably it is for a pair of compounds to be an R pair?  

Note: This may be a silly question to all chemists, but not for me, i am a computer science student , and my research field in bioinformatics and so i have to study both biology and bit of chemistry, so please just dont close the question or be harsh on me, I have very little knowledge in chemistry and also googling doesn't help much. I asked this question in Biology forum, they closed the question and asked me to ask it here





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> And does [*the score*] signify the bonding strength of how probably it is for a pair of compounds to be an R pair?
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No, it has nothing to do with that. It is not about how probably a particular reaction is.


When comparing **RC**s (reaction classes), the scores in the table of related reaction classes are just a measure on how similar these reactions are. 


`RC00064` apparently is an N-acylation or the formation of a peptide bond. `RC00197` with a score of `1.0` is a N-formylation and considered very similar.


Change the cutoff to a lower value, such as 0.4, and compare the results at the end of the table with `RC00064`. You'll find dissimilar reaction classes like `RC02518`, the oxidation of a selenol to a selenic acid.


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