Sum child elements of a collection

I am trying to get totals of all columns from a simple table. To do this I am trying to use the collection and just sumOf() for all of the elements, but it does not want to play nice.

I was thinking I could just use the passed in query collection and :

$theTableObject->sumOf(‘value’);

But it looks like there are parent values “element” which are stopping that from working??

‘Element 0: {
“id”: 5,
“title”: “a title”,
“type”: “a”,
“value”: 2800,
}’
‘Element 1: {
“id”: 4,
“title”: “a title”,
“type”: “a”,
“value”: 2100,
}’

Any ideas would be appreciated.