VTune Call Graph Profiler uses hardware tick counter to measure time. Because Microsoft Windows does not allow this counter to be virtualized this counter keeps running even when profiled application/thread is switched off from processor. So, actual measurements depends on your machine load. If you want to measure time as precise as possible, shut down all applications that you can before the measurements start.
In addition to this I would like to note, that time values, produced by Call Graph profiler are considerably less precise than those from Sampling profiler. The reason for this is that Sampling profiler'soverheadalmost not depends on application behavior, while Call Graph profiler's overhead is a constant per each call/return. This means that self timeof small functions/methods can be even less than overhead time of profiling routines themselves and measurements for short functions are less precise that for long.