The first survey is hundreds of questions and is what you are being paid to fill out, essentially. It can take anywhere from 30 minutes to a few hours, if not more depending on the pay rate and assignment. Generally I would expect to spend 1-2 hours on an average dining assignment from them, but the average dining assignments I've done might be different than the ones you've done, so it may be shorter or longer.
After you complete that survey, a new survey with, as said above, 10-12 questions appears. The survey is really simple to fill out and takes less than 5 minutes to do. Coyle is VERY clear that this five minute survey is in addition to the full survey that you have to fill out, it says something like:
This client requires that a benchmark survey be completed *****post-evaluation.***** This survey takes less than 5 minutes to complete and contains no narrative or comments--checklist only.