A&M Form Table Field Submission
I know I'm a bit late to this, but I think it's because your {{ loop.index }} is not 0-indexed, which is necessary for the array.  It should look like this:

&lt;input type="hidden" name="fields[selections][{{ loop.index0 }}][col1]" value="{{ item.qty }} x {{ item.description }}"&gt;

You also need an extra valueless hidden field above the loop to collect all the values into one array:

&lt;input type="hidden" name="fields[selections]" value=""&gt;

You can see a fuller example on how to format the HTML for all fields of all types on this StraightUpCraft page.  Scroll to the very bottom for tables.