Sum then average of an array

I'm trying to calculate the average backlog age of items in a freeform board from the vtb_card table. I'm grabbing the sys_created_on date, converting it into seconds, and then converting that into days, before putting it into an array.   What I seem to be stuck on is the summing the value of the array.   It doesn't actually appear to be adding the values together, but instead merging them.

I'm sure there is probably an easier way to do this, but this is what I have. I am not a coder by nature (or nurture).

// Get Today's Date
var today = gs.nowDateTime();
var dc = new DurationCalculator();
// Query for cards in the backlog
var age = new GlideRecord('vtb_card');
age.addQuery('board', '189201660f6b5e0032de6ab8b1050e7f'); // Deskside
age.addQuery('lane', 'b80401660f6b5e0032de6ab8b1050e49'); // Backlog
age.addQuery('removed', 'false');
age.query();
// Initialize the array
var holdThis = new Array(0);
// Loop through and list the backlog items
while (age.next()){ 
var created = age.task.sys_created_on;
var seconds = dc.calcScheduleDuration(created,today);
var calc = (seconds / 86400).toFixed(0);
   holdThis.push(calc);
   gs.print('Task: ' + age.task.number + " Created: " + age.task.sys_created_on + " Duration (seconds): " + seconds + " Days Open: " + calc);
}
// Print the array
gs.print("Array: " + holdThis);
// Sum the array
var total = holdThis.reduce(function (a, b) {
   return a + b;
}, 0);
// Average the array
var avg = (total / holdThis.length);
gs.print("Total: " + total);
 gs.print("Length: " + holdThis.length);
 gs.print("Average: " + avg);

Here is the output:

*** Script: Task: PTSK0002271 Created: 2017-04-26 15:02:07 Duration (seconds): 3810600 Days Open: 44
*** Script: Task: PTSK0002272 Created: 2017-04-26 15:15:01 Duration (seconds): 3809826 Days Open: 44
*** Script: Task: PTSK0001826 Created: 2017-01-25 18:40:13 Duration (seconds): 11659914 Days Open: 135
*** Script: Task: PTSK0002297 Created: 2017-05-04 14:22:12 Duration (seconds): 3121795 Days Open: 36
*** Script: Task: PTSK0002366 Created: 2017-05-19 17:54:19 Duration (seconds): 1813068 Days Open: 21
*** Script: Task: PTSK0002094 Created: 2017-03-14 12:09:14 Duration (seconds): 7536173 Days Open: 87
*** Script: Task: PTSK0002209 Created: 2017-04-12 16:30:52 Duration (seconds): 5014875 Days Open: 58
*** Script: Task: PTSK0001926 Created: 2017-02-10 15:43:14 Duration (seconds): 10288133 Days Open: 119
*** Script: Array: 44,44,135,36,21,87,58,119
*** Script: Total: 0444413536218758119
*** Script: Length: 8
*** Script: Average: 55551692027344770