Unlike bit rate between M3 and PC

Hi all,
I don't understand why my M3 display quailty of song different from my PC.
In M3 display sample rate = 24khz & bit rate = 144 kbps,
but in my pc show sample rate = 44khz & bit rate = 320 kbps.
my format songs are mp3

explain me please,
thanks in advance

I think this might be because of VBR MP3, do you use them?

i thought of that too... it would explain the jump in KB but not the one in Khz right?
VBR doesn't have a variable Khz but a variable bit-rate