Which is like saying "That family is spending 52% of the money it doesn't spend on rent/mortgage, food, and fuel on guns and ammo." Doesn't really tell you a lot if you don't know how much they're spending on rent/mortgage, food, and fuel.

Also, discretionary here is entirely a political/legal term.

I think one would find it very hard to argue that military spending is discretionary for any major nation in the layman sense of that word, even if the US's military spending is beyond control (on the flip side, the US also gets much less value for its military spending relative to say the value China gets for its military spending).