Is there a way to tell what public beta you're running?
Go into the menu 'About this Mac'. Under 'OS X Yosemite' click on 'Version 10.10' - right beside, the build number appears in brackets then.
OS X 10.10 Yosemite Public Beta 1 - build 14A297a
OS X 10.10 Yosemite Public Beta 2 - build 14A329r
OS X 10.10 Yosemite Public Beta 3 - build 14A361p
OS X 10.10 Yosemite Public Beta 4 - build 14A379b
OS X 10.10 Yosemite Public Beta 5 - build 14A386b
OS X 10.10 Yosemite Public Beta 6 - build 14A388b