Sometimes folks will slightly fatten or skinny a dose so its just a hair more or less than the quarter unit marking. So you might see if a fat 3.0 might work after you drain the depot a tad with a regular 3.0 unit dose.
The other option is to tweak the carbohydrate level to work with the dose - can you go any lower on the carb level to work with the 3.0 unit dose? One way to reduce the carb level if you're not at nearly 0 already, is to add 1 ounce of plain meat or poultry to 5 ounces of cat food, mix well, and portion out (per Cat Info).
Or, perhaps you could go a hair higher on the carb level to go with the 3.25 unit dose?