I'm surprised the total mode is even available in a gauge chart. A gauge chart has no dimensions, no rows, so setting it to "sum of rows" honestly makes no sense to me. I'd think it would always function as if "expression total" was selected. Sounds like it is, so I guess it's working as I'd expect, and I think it just shouldn't let you select anything else.
To solve the problem, you'll probably have to do a sum of rows manually. Aggr() lets you simulate a table with rows. I don't know your dimensions for the table you like, but for the sake of argument, let's say it's Field1 and Field2. You should be able to simulate sum of rows by replacing your gauge chart expression with this:
I have a similar problem to the one you've assisted with above. I was wondering if you could assist on this. All I need to do is divide the sum of Total_proceeds by the sum of Market_Value. The way I'm currently doing it, gives an incorrect total. My expression is: