Insert a string of numbers as an array into database from multi check box form

I have a form that has dynamically generated check boxes. Seems like it is sending the data to the action script correctly. Each check box has a value and i want to add all of the values of the check boxes to a single string field such as: 1,6,8,23

I’m guessing I’m missing something with the array config?

Here is my form:

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Here is my action script

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and here is the update portion of it:

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