Esun Order Number
Generates order increment IDs from one atomic sequence per Magento Website.
Configure Stores > Configuration > Esun > Order Number after
switching the configuration scope to the target Website. The generated format
is Site Name + Number, for example US100001.
First Order Number initializes a Website only when its first order number is
reserved. It deliberately does not reset a sequence that has already started.
Invoice, shipment and credit memo sequences are unchanged.