How to sum expression at higher group level

I spent hours figuring this out without coming to a solution. How can I sum the totals at Group 1 (G1) at a higher group level (G2)?

anyone can point me to the right direction? The values in the first column (4391, 4375, etc.) get returned from the stored procedure and represent the totals for each specific group. The values in the second column represent a unit value and can be of different amounts. In the example above they all have the same value. In the detail section (suppressed in my example) i do NOT get 4391 records for group 1 and 4375 records for group 2, etc.

Thanks so much for any help.