Why is the marking on the runway written as (9/27) Telluride (KTEX), Colorado, USA. whereas the direction is 284 degrees? Shouldn't it be (10/28) instead?
That direction (284) is the true heading, but runways are numbered according to the magnetic heading.
Runways are usually numbered according to their direction, more precisely called runway magnetic bearing or QFU (see Q codes). (How are runways numbered?)
276 magnetic, 285 true
096 magnetic, 105 true
While 276 should be rounded to runway 28, it could be a recent change that the magnetic heading changed to 276 from say <275. There is a process to go through, so a recent change in magnetic variation does not mean the renumbering will swiftly follow.
Every five years, the FAA reevaluates shifts in the pole—its magnetic variation—and makes changes to runways and flight procedures as needed. (How do airports determine when they should change their runway numbers?)