Hi Johbo,
There isnt a easy answer on this and your information is incompete.
823 STP packets in how much time?
A STP packet is a BPDU packet and is send per spanning-tree instance (or by cisco per vlan with PVST+). So how more instances you have, how more BPDU packets will send through your network :).
Normally i see one STP packet per spanning-tree instance per seconde.
Then time is an important factor, so how long is your capture?
But in fact... A STP packet is small as 480bits x 823packets brings you up to 395Kbit of data, and that is 49Kbyte of data :).
But before deepdive in packet analyze you should better look at the STP logs of your switch.