I recently managed to get FC Silver with a return Ecomony flight to EWR. I was on 12 points prior to that return flight and earned 4 points on it - which should have taken me to 16, hwoever according to the VS website I seem to have lost the last point as my count has reset to zero - is that what happens on transition. I was kind of hoping that would mean just 9 points to retain silver, but it says the full 10 are needed.
Yes, your points are reset when you hit silver.
The tier points system is quite well explained on the VS website - here.
There was an even better explanation on the old site provided by our own Richard Mannion on the old site, but I can't find it now.
Nick