This is easy.
The tricky part is that the material for each surface comes after the surface. Thus, in our case, the material for the OBJ surface is just air.
The material for the next surface (the AST surface) is the glass that the lens is made from
The material for the next surface is air again!
Once again, you don't have to worry about the last surface and can leave it as air.
So, the table describing your optical system is