why the same path have different clock delay ?

Within a given timing model(say slow 100) there are two sub-models, a slow and fast sub-model. This accounts for the fact that even if the die is at a given corner, individual paths will vary, which is generally called On-Die Variation. When doing setup analysis on a path, the Data Arrival will use the slow sub-model and Data Required will use the fast. This then flips if you do hold analysis on the exact same path.

But in your case, it's a single clock path, how can it vary? It can't, which is why a thing called Common Clock Path Pessimism Removal will remove this variation. If you scroll further down the Data Required Path, you should see a line-item call pessimisim. It is added to the Data Required Path, which helps timing(makes the slack better), and counteracts this on-die variation modeling on a common clock path.

On alterawiki.com there is TimeQuest User Guide I put together that talks about this. (Although it's not a lot more than what I've said here.)