PowerQuery / M - Calculate total of multiple values

I have two tables,

Table A (list_backup) has multiple entries for each key, table B (list) has single entries for the key.

Table A has a column 'called_count' that I would like to sum and add to a column in table B, per key

In the example below I need to calculate the column highlighted in red, totalCall.

I can do this in DAX but I need to use TotalCall on an X axis and so need to calculate it in my query instead.

Can anyone help, I thought I'd found a solution here but I'm struggling to understand how to modify it to apply to my data.