Of course I can. There is no difference in surface area.

However, there is definetly a larger surface area than if you were to simply fold the paper twice and place it flat against the sides of the funnel, do you agree?

As I learned that in secondary school and demonstrators in my university, one of the advantage of increasing the folds of a filter paper will give a higher efficiency of diffusion by increasing the surface area.

I wonder know how can it increase the surface area?

Their surface areas should be the same I think.

Assuming "R" is the radius of the filter paper, no matter the no. of folds it is, the length of the folded paper is also "R".

OK, if there are 2 filter papers (+ 1 funnel each), one is 8-folded, another is 16-folded, when the mixture is poured into them as same level, for example 1/2R, their areas are the same (assume there is no overlapping between each folding section), am I right?

One thing I want to point out is that, as the folds of filter paper increase, the volume of the cone (just imagine it looks like a cone) decrease, do you agree?

You can see that the cone is smaller and the angle of it is also smaller than less folded one.

For same area but difference in volume, therefore, the surface area to volume ratio increases as no. of folds of filter paper increases, just like the case of diffusion of red blood cell that why it is biconcave in shape. This give a higher efficency of diffusion (filtration).

Do you agree?