When using PieSync in Command, what happens if I sync more contacts than I’m allowed to sync?

PieSync subscriptions work with pricing tiers. Every pricing tier is linked to a maximum amount of contacts you can sync for that amount. You can find the pricing tiers over here by moving the slider

If you are subscribed to a certain pricing tier and sync more contacts then it allows, you’ll be upgraded to the next applicable pricing tier. This subscription upgrade will happen automatically, but you will be notified 5 days in advance by email. During those 5 days you can adjust your connections in case you don’t want to be upgraded, or you can do nothing in case you don’t mind it.

If you don't want to get upgraded you will be required to decrease your contact count. You can do that the following ways:

• Apply additional rules and/or filters to your current connections. By adding filters you can have fewer contacts matching your connection rules, your contact count will decrease as PieSync will keep fewer contacts in sync. 
• Delete a connection. You are being billed for the total number of contacts across all connections (minus your free connection). So by deleting a connection, your contact count will also decrease.
• Deleting contacts. If you delete contacts, PieSync will have fewer contacts to keep in sync. Do bear in mind that PieSync doesn’t always know when you’ve deleted a contact. So the count may not always be affected. In Command PieSync does recognize deletions though.