Analyzing routing delay added for hold timing

The numbers you're seeing are very common, and I don't think you can really go much below that. Note that the 23us is higher than you think, as that's accumulated across multiple paths, e.g. a single amount of delay added can be counted many times. I also believe its' counting against the "ideal" route, e.g. when the router first starts and everything can use ideal resources(but it's illegal, since routing wires can be used more than once). So a lot of the numbers are high.