1l of linseed oil paint is enough for about 12-15 sq m,
if it is a completely clean surface you are going to paint, you should paint 3 layers!
If you have, for example, an area of 4 sq m to paint, 1l of paint is enough for your project, if it is an area you are going to touch up, 1-2 layers of new paint are usually enough, depending on how worn the surface is!