You can't calculate pi to the last decimal place, no computer ever made has been able to. 3.141 is a documented constant for the value of Pi, the one contained it the framework just goes a bit further than that.
I believe the current record is...
68,719,470,000 decimal places.
Computers have a 'built in' safety measure that it would only calculate pi to a pre-defined number of decimal places, otherwise they would run out of memory.