Why is the bitrate different from what was selected when recording?

Question

Video processing

I use Bandicam for recording.
Actually, the question itself is why, when specifying the bitrate after recording, a significantly lower bitrate is indicated in the file properties?
Let's say: When shooting using H.264 (X264) with a constant bit rate (CBR) and its value of 35000 kbps, as a result, after shooting, the file properties show a value in the region of 24-26 thousand kbps.
In addition (important) when trying to record with the same settings but with a higher bitrate (50,000 kbps), after recording it turns out that the recording has an even lower bitrate than in the case I described above: 18-19,000 kbps