Exclusing travel to North America, the MSC is based on check in to bag collection
Since there is no baggage check through on Jetstar, then will be JQ's allowance for JQ check in and QF's allowance for QF check in

If your baggage allowance on your ticket is showing as 1 piece x 23 kg, then that is going to be the allowance that you have

If you only need 25kg, I would look at whether you can get rest in carry on allowance rather than paying excess baggage fees for exceeding 23kg