1 A retired Regular officer who also is employed by the federal government and is subject to the dual compensation statutes may have that reduction reduced because of the waiver of retired pay to receive VA benefits.
If they don't, then 4 thick is usually standard for a patio slab, how large or small it is doesn't really matter. The most important part is the sub-base. Make sure you have a good gravel base. I would recommend at least 12 inches of compacted gravel. I like gravel where the aggregate (rocks) are no larger than 1.
All 3 types of slabs will need a footer and a slab of at least 4 thick. The footers depth needs to be the depth of the frost line or as per local code, but no less than 12 deep. The width of the footer needs to be at least 12 wide. Here you can see illustration of all 3 styles of slabs for a Coast to Coast Carports built Garage that is a 24' wide by 30' long (24x30).