It is strongly recommended you wait out half of your punishment before making an appeal.
You have 8 days remaining until you'd be free to appeal at the half-way mark.
As others have said, you can make one whenever you want, but a huge majority of appeals made in the first half of a punishment are usually not accepted or even considered.
Disputes do not follow this logic and can be made immediately, however they are entirely for challenging the validity of a punishment and thus require evidence to prove it wrong.