The age of the universe is 13.798±0.037 billion years, yet the age of HD 140283 is 14.46±0.8 billion years, how this can be the case?
It's down the fact that different properties are used to calculate the ages and if you look at the margin of error in the calculations they're not incompatible.
The lower limit for the age of HD140283 is:
which is within the range for the age of the universe.
Once better measurements of HD140283 are made it's age will probably be revised to a more "sensible" figure that matches more closely the age of the universe.