On the Audience Introduction Report, in Demographics Highlights, we are showing the composition for the highest indexing attribute value in a set list of attributes. For example, our Auto Intenders audience over-indexes on being aged 35-44 (for which the composition is 25%) with a Household Income of $150K+ (for which the composition is 14%).
Note that these are not the attribute values with the highest composition for that attribute, but the composition values for the attribute values with the highest index. For example, if we look at Auto Intenders on the Audience Comparison Report - we can see that the attribute value that has the highest composition household income is $25-50K. But those are not the attribute values that over-index.
Looking at the Bar Chart and household income insights, we can see that, for Auto Intenders, the highest indexing value for household income is $150K+.
Long story short, the Audience Introduction report helps save you time analyzing by showing you the attribute values that over-index, and then what their composition is.