Question about finding your Rem Circle

I want to find out my Rem phase to get a good time for a WBTB since i've never had luck with the normal times(4h-6h). I tried the "Drink water before going to bed" method last night and it worked. I felt asleep at 1:00am and woke up at 3:20am.

Now my question: Should i wake up after 2:20h(+ about 15 minutes to enter the next dream) of sleep for a WBTB? Or should i try it again and try to catch the other Rem phases because i've read that there are many Rem phases and the last one's are the best to get lucid.