This may be covered in the owners manual, I haven't checked yet, but the buckets over the valve spring and shims are color coded and different thicknesses. I noticed a little dab of paint on the inside of the buckets, mine were green and yellow. I know that on multicylinder engines Honda color codes (or used to when I was racing 20 years ago) connecting rods according to their weight. When replacing a rod in a 4 cylinder street bike you have to check the color and order the same to keep the engine balanced. I checked the thickness of the buckets, where they sit on the shim, with a micrometer and sure enough the yellow dot buckets were thicker than the green dot buckets. The manual does say to keep the buckets in their original position and it's always a good idea anyway since things break in and wear a certain way. If you accidently mixed up your buckets after your shim calculation, you could throw off your clearance. Of course you're going to recheck the clearance after assembly if you did change shims so you'd catch a problem, but if you reassemble without changing shims you might not check. If the buckets get crossed you could have trouble. If this is common knowledge or it's been covered before feel free to point that out.