A modification structure

[pdh0224]

Dear teacher,

Another company that follows national eating trends, NPD Foodworld in Chicago, reports that the biggest cereal consumers last year were children between the ages of 6 and 12, with 87 percent of survey participants in that age group eating cereal at least once every two weeks. But the teenage population (ages 13 to 17) was close behind, at 80 percent.

Q : I think "with 87....two weeks" modifies "children" ,and The information shows the result of the survey.
Am I right?

[Alan]

It is a prepositional equivalent of a nominative absolute, serving similarly to furnish additional information ( = AND 87% were...).
Yes, these are the survey results.