I'm sure you have a reason for wanting them in the same order, so here's a way you could do it if it's that important.
Set the option for "Set Invoice # Same as PackSlip". Then release the orders in the order you want. This assigns the next Invoice Number as the Pack Slip number in the order you release the SOs.
From the Web Help page
Quote:Set Pack Slip Same as Invoice
If this is set to Y, then when releasing sales orders in SO-E Release Sales Orders the same number (the Next Invoice Number) will be assigned to the order for both the Invoice and Pack Slip number. This eliminates having 2 sets of numbers and also enables reprinting a pack slip after the invoice has posted because it can pull from the posted invoice file for the data since it is a one-to-one relationship.