On the yearly Standard plan, you pay $6.67 per user/month instead of $8 on the monthly plan.
You'll be billed once for the entire year when you're upgrading (ie. If you have 100 users, you'll be billed 100*6.67*12 = $8004).
When you add new users, we'll send you intermediary invoices based on the remaining period of your contract. (ie. If you add 30 new users during the 2nd month, you'll receive an intermediary invoice at the end of the month based on the 10 remaining months of the year (30*6.67*10)).
A yearly plan is a one-year commitment. Any cancellation made during the year will only be taken into account once that year is over.
Your plan will be automatically renewed at the end of the year unless you cancel your plan before. You will be notified by email before this happens.