Of course I asked the bot about the number, it replied as below. If what it says is true, it's not as simple as a scale from 0=Mellow to 100=Frenzied, it's an index of how representative each style is of the genre it falls under — which would be an odd way to want to see things sorted, no? My confidence in ChatGPT as a BIAB "expert" is not high at the moment. Be that as it may...

CHATGPT SPEAKS:

"Genre Intensity Score" in Band-in-a-Box refers to a feature in the software that assigns a numerical value to the level of genre influence in a musical composition. This score indicates the style and genre of the music being played and helps users to categorize and organize their music library. The score ranges from 0 to 100, with higher scores indicating a stronger presence of a particular genre in the music.