Hi Batou,
You can interpolate hairs using only 20 guides or even less. You are getting only 20 hairs in render because in your third step you are selecting Guides As hairs for Distribution type, so 20 guides = 20 Hairs. To create more hairs you have to use another distribution type in MeshFromStrands like Random Area, Uniform, UV Distribution or whatever feed your needs, then in the Guide Interpolation roll out find the better convination of Interpolation and Guide Count. I hope this helps.
Jeordanis Figuereo (Product Designer. EPHERE Inc.)
