Pulling information from a logging field

I am trying to pull information from a multi-line text field that is logging each entry. I don't need the first or last entry in the field.  I need the 3rd entry.  I know how to get the first or last one with formula but cannot figure out how to do the 3rd entry.  I have a field that will count each time an entry is added. I just need the date of when it was logged.
Here is the formula from the field that is counting the entries in the logging field:

var text Dispositions = [Log Disposition];
Count(
Part($Dispositions,3,"]"),   
Part($Dispositions,4,"]"),
Part($Dispositions,5,"]"),
Part($Dispositions,6,"]"),
Part($Dispositions,7,"]"),
Part($Dispositions,8,"]"),
Part($Dispositions,9,"]"),
Part($Dispositions,10,"]"),
$dispositions)

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Nicole Varner
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