I have been trying find some documentation that describes how the sample rate works during event mode.

for example the following line:
sudo opcontrol --event=PC_BRANCH_MIS_PRED:10000:0x0:0:1

This sets the sample rate at 10k.

1) does this mean it samples at 10k clock cycles or 10k ticks or other?
2) what does a sample mean. The way I understand performance counters is that they count the occurrence of a specific event regardless of what program caused it ... right? How does oprofile "sample" an event that might have occurred several times in between the sample rate and assign that sample to a program? The counters on ARM I believe get set to an event, started, and stopped later in time. I think the values are absolute and not statistical. 

Thanks for your time,