That car was configured with two manual tranmssion options
g35mr – capacity is 3.03 quarts
a26mr - capacity is 2.6 quarts
So maybe you have the first one, which would take more to refill it. In any event provided you are using the correct fill hole – which I expect you are – and you don’t feel the oil through the fill hole after driving the car a few miles to get the oil to redistribute the oil, then just buy another bottle of trans oil and top it off. Usually the amount of anglular tilt involved when jacking the car up doesn’t cause enough error at the oil level fill plug to worry about. If you can feel the oil inside that hole, insert the plug and you are good to go.
BTW, me, I’d only use the exact transmission gear oil as spec’d by Mazda.