A GED Ready® voucher can be used once for any GED Ready subject test. So, if you want to take 4 subtests, you need to have 4 vouchers.
Also, if you want to repeat your GED Ready test, you must get a new voucher code.
If you have the Onsego30 plan, you can download 4 vouchers for free.
You will be using the Onsego webpage because Onsego30, the super-fast-track course, falls under the Onsego GED Prep umbrella.