i am making a 70 number cake for a ladies birthday. I am using a 12x 18 cake pan. The numbers will be cut out . How many people does this feed? it will be a single layer or should i make it a double layer?

I am trying to visualize a 7 and a 0 carved from a 12x18 and to be honest, don't have a clue, but suspect not many.
How many do you need?
Is the cake to be the only food offered?
If more than 10 -15, how about mounting the numbers on a sheet cake or making a dozen or so cupcakes with cute little 70 toppers to satellite your main cake?

I did one for a client recently. I made two 12x18 cakes (one for each number). Then carved the numbers numbers. Also, the cake is single layer. I can't remember how many servings. I usually give a range and let customers know it depends how large the slices are cut. HTH

edit to add - tried to attach photo, but didn't work. It is in "my photos."