You're a newlywed...learn to pick your battles. If you've both agreed on the amount being saved, and that is happening automatically, and you have money for bills, I wouldn't jeopardize a happy marriage over it, especially when you haven't built up any 'goodwill'.
But, there are things that you can extrapolate from your spending and optimize. For example, is there a lot of packaged items (chips, cookies, crackers) coming into the house, expensive flavored water or other fru-fru type groceries, this would be a place to optimize. Also, you know how many times you're eating out and about how much it costs. You know if you both are packing your lunches each day or not. You know if you're doing a lot of extra driving. You know if there are a lot of new things showing up in your home, such as new bed sheets, lamps, and placemats. You get the idea. Even without knowing all of the nitty gritty details, you can still tell where to optimize. Over time, you can start to increase the savings, and that is the really important part in the early days.
I bet you can guesstimate your % saved pretty well, and it will be directionally correct. Don't sweat this, it's not worth it.