Yes. This can be done in the program under invoicing settings.
For example, if you switched to Procountor Solo from another invoicing tool, you can continue the numbering from where you left when you implemented the program.
However, the invoice numbers can only be made larger if you already have sent some invoices in Solo, because otherwise the program might have duplicate invoice numbers.
Set your preferred invoice number in the program Settings under Invoicing settings > Next invoice number