How to interpret dropped packets numbers?

Hello!

I have a simple question concerning the log output of bro in terms of dropped packets. In my logs I find lines typically looking somewhat like the following:

1226932503.913993:DroppedPackets:NOTICE_ALARM_ALWAYS:::::::::::762 packets dropped after filtering, 27140 received::@f1-2fa2-4a
1226932513.914576:DroppedPackets:NOTICE_ALARM_ALWAYS:::::::::::762 packets dropped after filtering, 25282 received::@f1-2fa2-4b
1226932523.915773:DroppedPackets:NOTICE_ALARM_ALWAYS:::::::::::762 packets dropped after filtering, 28475 received::@f1-2fa2-4c
1226932533.915773:DroppedPackets:NOTICE_ALARM_ALWAYS:::::::::::762 packets dropped after filtering, 29652 received::@f1-2fa2-4d
1226932543.915927:DroppedPackets:NOTICE_ALARM_ALWAYS:::::::::::762 packets dropped after filtering, 23517 received::@f1-2fa2-4e
1226932553.916319:DroppedPackets:NOTICE_ALARM_ALWAYS:::::::::::762 packets dropped after filtering, 25519 received::@f1-2fa2-4f
1226932563.916847:DroppedPackets:NOTICE_ALARM_ALWAYS:::::::::::1181 packets dropped after filtering, 42911 received::@f1-2fa2-50
1226932573.916864:DroppedPackets:NOTICE_ALARM_ALWAYS:::::::::::1181 packets dropped after filtering, 24068 received::@f1-2fa2-51
1226932583.916923:DroppedPackets:NOTICE_ALARM_ALWAYS:::::::::::1181 packets dropped after filtering, 23854 received::@f1-2fa2-52
1226932593.916972:DroppedPackets:NOTICE_ALARM_ALWAYS:::::::::::1218 packets dropped after filtering, 26452 received::@f1-2fa2-53
1226932603.917322:DroppedPackets:NOTICE_ALARM_ALWAYS:::::::::::1218 packets dropped after filtering, 23351 received::@f1-2fa2-54
1226932613.917342:DroppedPackets:NOTICE_ALARM_ALWAYS:::::::::::1218 packets dropped after filtering, 22009 received::@f1-2fa2-55
1226932623.917497:DroppedPackets:NOTICE_ALARM_ALWAYS:::::::::::1218 packets dropped after filtering, 24184 received::@f1-2fa2-56
1226932633.918049:DroppedPackets:NOTICE_ALARM_ALWAYS:::::::::::1218 packets dropped after filtering, 22079 received::@f1-2fa2-57
1226932643.918297:DroppedPackets:NOTICE_ALARM_ALWAYS:::::::::::1218 packets dropped after filtering, 24630 received::@f1-2fa2-58

Obviously, every 10 seconds bro outputs a line with dropped packets information. Unfortunately, I am not sure about how exactly to interpret the numbers. Are they total counts since the beginning of the current bro execution, are they per 10 seconds timeslice, or something even different? I am confused by the fact that the dropped numbers are often the same but never decrease (which points towards a total count), and on the other hand the received numbers behave differently.

What exactly does "received" mean? Does this include the dropped packets? I.e., do i need to subtract them if I want to know how many packets have actually been handled and processed by bro?

If I wanted to calculate the percentage of dropped packets over the period of a log-file, how would I do it?

Regards,
Peter.