I actually tested this theory out. Tim is ONLY denied Read/execute access in this case. He will still have the other privileges that are granted to an administrator. If he is attempting to write to a file, the first time write is found won't be on Tim's explicit ACE, it will be found on Administrators, no matter the order. 

Try it yourself. Add the group `EVERYONE` with full permissions and then add `Guest` denying only Read/List/Execute. Switch over to Effective permissions and select Guest. Note what those are.