The billing date shown on your invoice starts the day you subscribe to any of the plans in Stock Sync.
Stock Sync fees are charged on the standard 30-day invoice cycle that begins when you start your subscription.
Stock Sync charges are pro-rata. So users would not lose the time in their current plan. And the limit will be raised according to the plan if they choose to upgrade their plan.
NOTE: Total variant(s) is not the same as the total product(s)
Stock Sync by default will take all variants on your store to find the matching SKU.
That translates to more variants on the store required more memory and processing power to process and find the matching variant.
If you have only 50 products and about 300 variants, you only have to pay $5 per month. You may reduce the number of variants loaded by applying Filter by Shopify products.
For example, a store has products under Brand A and Brand B. Brand A has total variants of 100 and Brand B has total variants of 20. If the Vendor filter includes Brand B only, it will only process 20.