I am in the Petroleum Measurement Business and have done a bunch of MM 2700 Set ups. I don't have any experience with RSL5000 but maybe I can help based on my experience with RSL500.
In RSLogix 500, you click on "Function Files" under the project tree. Then click on the HSC tab. All the High Speed Counters you have available based on the processor will show up there. You click on the + to expand the file. You then fill out the info. The most important info is the PFN - Program File Number. This is the sub routine that executes when the counter is done. CE - Counter Enable put a 1 here. And HIP - High Preset put 10,000 here. So every time the HSC counts to 10,000 it will execute the subroutine you selected in PFN.
Make sure that the input filter for the channel is set to the lowest setting possible. With the pulses coming in at 10,000 per BBL if the input filter is set too high you will end up missing some.
The next thing to keep in mind is if you need 10,000 pulses per BBL? Are you using this pulse stream for custody transfer? Are you sending them to another flow computer or are you using them for proving? If not I wouldn't mess with a pulse rate that high. I would go with 1,000 pulses/BBL. That will give you a high enough resolution to measure accurate enough.
I have been in the Measurement Business for 22 years so if I can help let me know.
Chris