The Shopify Order Printer app (in which our templates are used) does not support sequential invoice numbers by default. 

However, it is possible to do with a small change to the template code. The way to do it would be to find this code in your template:

And replace it with:

Note: You must replace the xxxx in the above code with the correct number to start your sequence.

The order number starts at 1 for your first Shopify order, so you minus the needed number to get your correct number series.