Direction of cover glass thickness to use From specimen to eye-piece is recognized as an optical system. So the cover glass is a part of optical system and the slide glass is not. To extract the full performance of objective lens, you should use the best quality cover glass as possible. If your lens has 0.17 marking, that means this lens exhibit its full ability by using 0.17mm thickness cover glass. Good quality cover glass has specification list on its box and consistency range.
Rest is the same.
These notation may be slightly different by each manufacture. I recommend you to use 10x or lower wide field eye-piece. First, objective lens enlarges the specimen by its power and makes a virtual image. Eye-piece works to enlarge this virtual image and leads the further enlarged image to your eye. It is often thought that higher power is better but it is not always true.