Pull values from field in multiple records into a formula field using queries

I am building a formula field that needs to pull-in values from multiple records. It would pull-in the "# of Organic Users" field value from records that have a `created date` value that are during the last 6 months. The data will be displayed in the embedded bar graph (see attached screenshot below), which is a formula field built from basic HTML and inline CSS. Each field value mentioned previously would be represented as a bar in the bar chart. I'm not well-versed in querying other records/fields, so any help would be great, thanks!

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Matt Makris
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