You can rank your tables in advanced table settings. simpleERB will by default assign tables in numerical order, providing the table has the capacity to seat the booking. However, you might want Table 8, which is next to the window, to be allocated first.

To do this, just go to table ranking and move the tables around until you have an order that works for you.

If you want to drill down even further into your seating allocation, you can prioritise your table ranking by cover amount.

Here you select the cover size and then individually choose which tables are allocated first for that cover amount. 

The ranking and prioritise options both allow you to rank table joins which you have created.