Fokker 100 impossible speed?

Hi, I'm a total rookie here, so apologies if this question has an obvious answer.

I've been tracking a Swiss Fokker 100 from Birmingham to Zurich, and on crossing the English Channel, the speed registered was 619mph. However, maximum cruising speed of the aircraft seems to be 525mph.

So was it going well beyond the maximum, or perhaps there's some discrepancy somewhere?

Thanks,

Ken