what does the s mean that goes up each time
what is the totally amount of indices for this model?
s stands for smoothing groups, meaning that vertices that are a part of a smoothing group use the average of the face normals of the faces that it shares. A cube for example would consist of 12 trianglular faces, and 6 smoothing groups, because the triangles of each side share the same normal.( note: 0 smoothing groups also work, because the averaging of face normals will result in the same normal as the face normal that each vertex belongs to) If you wanted a half dome, the faces on the flat disk at the bottom would belong to a group(again: or not because they all share the same normal anyway) while the hemisphere vertices would belong to a smoothing group(this must be done, to get the normals correct. If your familiar with blender, it is the difference between flat and smooth shading.
the entire model needs to be parsed to be sure how many indices are in it, as vertex data may or may not be shared by several faces, and if they belong to separate smoothing groups, they will need to be duplicated in the mesh.
for your mesh, parse the vertices into a temporary storage, since you have quads, you'll need to get triangles first. the winding order will tell you which way to split, and also help calculate the normal. for each smoothing group, for each face you process, add its normal to an std::vector for each vertex that is part of that face using the vertex number as the index., and increment a counter for each vertex did that to. At the end of the s group, your counter will tell you how many faces that vertex was part of, divide your normal by that, and that will be the normal to use in your mesh. push those processed verts into your mesh with indices, reset the counters, clear the normals and parse the next group