Grilling relies on many different things affecting the end result: the quality of coals, the cooking device, weather and quality of ingredients, so timings vary and are not set in stone. Rule number one is to stay with the robata throughout, as some dishes cook in a matter of minutes, or need rotating, so no distractions!
Cooking on skewers is easier as all pieces are the same size and, providing the coals are stacked neatly, the pieces of meat should cook evenly. Follow the timing instructions in the recipes, but if in doubt use one skewer as a tester, cutting into a piece to check if it is cooked.