|re: "Afraid I could not follow instructions as totally new to this"|
New or not shouldn't matter. Do you see the little word pre above the reply box? Click it and see what happens. When it appears in your post, put your data between the > <. The instructions I gave are pretty straight forward.
re: "I want to identify how many Managers worked in the 24hrs"
You didn't give us very much detail to work with.
To answer your question, the answer is 1, which I determined just by looking at your example.
Manager 08:00 20:00 12
There's one occurrence of "Manager" and it appears he worked between 8am-8pm.
If you need a formula to count how many times the word "Manager" appears in your list, this would do it:
As far as the hours part goes, I'm not sure what you are asking for. Perhaps a few more examples of Input data and the expected Output would help.
For example, what answer (or answers?) would you expect based on the example you gave us?