If we upgrade from one subscription to another, will we be credited for the value of the time left on our current subscription?

What happens if I upgrate to the yearly bronze plan and later (before the year ends) I find out I need to re-upgrade due to submission volume. Would I only pay the difference for the upgrade or would I have to pay for the whole plan cost all together? 

Trying to figure out if I should go month to month or take advantage of the yearly sale. 

Best,

Jon

If you need to upgrade further, the value of the remaining time on any current subscription would be applied to the cost of the new subscription.  You would only pay for the difference between that value and the cost of the subscription.