Don't count. That defeats the purpose of it. Counting is left-brain, you want to turn off that hemisphere and delve into the eternal timeless right hemisphere.
You can begin it any time, or tomorrow when the Moon is Full in Taurus :)
I think that's ideal for me. I want to learn to be in the now and "do not think" because my left brain in addition to my natural powers of manifestation are manifesting literal illness which is breeding more panic, despair.
Only, I'm afraid, as @AFODO mentioned, it can have unintended consequences. I tried to search for all possible meanings in the Sanskrit dictionary and it looks like the Mantra connects you to a state of clarity and shattering illusions, serenity, like a still calm. The other user mentioned creation but I see this more in SATANAMA (where Sa means Birth). I don't know if that connects to Satya as well. I don't want this to enhance manifestation out of control, but maybe this is me being paranoid.
From my research on Sanskrit, I found
▶Watch on YouTubeExternal media opens in its original service.
This person seems knowledgeble in the sacred language and explains that "Sat" is the present participle of the word "to be" ("as"), whereas "ya" is a suffix (which means "related to"). I simply don't know all the applications of this mantra, though.