I assumed that the Javascript custom code for counting and limiting checkboxes was the same for checkboxes from a Dynamic Field, but nope. Codes are here:

Count:

https://formidableforms.com/knowledgebase/javascript-examples/#kb-count-number-of-checked-boxes

Limit: https://formidableforms.com/knowledgebase/javascript-examples/#kb-limit-the-number-of-checked-boxes

The way of referencing the checkboxes fields seems to be the same in both cases, native checkboxes and Dynamic field checkboxes:

$('input[name="item_meta[970][]"]')

They appear identical in the console explorer of the browser. But the code (both above) only works in native checkboxes. Or is something so obvious that I'm not seeing? I would appreciate some insight to this, because these are the little details that drive me crazy in Formidable.