Just keep it simple and explain that it is exactly what your question implies, the VP only APPEAR to reset to zero.
You never really lose your VP (except those that expire after 180 days) they are still all tallied for you on your VP Ledger.
The Scorecard Tab in our Affiliate Center is exactly that, it's a scorecard that let's you keep track of how you are doing each month and give you an idea of what your commissions will be the following month.