I see where the drawing went bad. They didn't take into account the margin when they chose the sizes. This is a case of not maintaining a constant reference. They allowed an 1/8" margin, witch is common. Ball bearing slides will always have some side to side play and if you make the face too close the finish will get dinged and look like sh**.
For ball bearing slides, especially the Chinese ones sold by HD allow at least a 32nd extra opening. That tolerance gives the draw glide an allowance of 1/64" for variances in forming the metal. Not a lot considering there are 3 parts that are formed metal.
I run a production shop and our standard margin is 1/8". Since we only make Euro type cabinets all hardware is installed before the case is assembled. A lot easier & faster than trying to install guides inside of a cabinet box. It requires a decent level of accuracy but there is no such thing as absolutely accurate.
Make some supports to rest your guides on when installing so they are perfectly parallel to each other.
From now on make your own plans, lesson learned??