This gets a bit confusing. We need 30mil between boards to get the router bit in. But, you can save some money by determining the overall square that your boards fit into.
Example:
Your board is 1"x1.6". Normally, this would be 2 square inches.
If you need 5 boards, add .030 to one dimension and multiply by 5.
1.6 + 0.030 = 1.630 * 5 = 8.15" - round up to 9". The total usage is 1x9" or 9 square inches saving you 1 square inch. A little savings in this small example, but it can add up!