The exam numbers are the particular pool of questions that are taken. Your certification in both cases is the same JNCIA-Junos.
Once you pass any currently authorized exam you will have the JNCIA-Junos certification for 3 years from that date. There is no effect when exam pools are changed.
My experience with vouchers is that they will work on the registration site up until the expiration date you have with that voucher so that should be fine with the exam number change.
Good luck in your preparations.