For the last two years, 1470 on the PSAT has been enough to get NMS in Florida, meaning top 1% PSAT scores.
The actual number associated with national merit is a composite of the 3 (Reading, Writing, and Math) sub scores (out of 40) x 2. This means each section counts equally - whereas for your PSAT score - Math is given the same weight as a combined Reading and Writing score.
In short - for National Merit - Verbal (reading & writing) counts for 2/3 of your score!
E.g. Reading 38 + Writing 37 + Math 37 = 112 x 2 =224
So the actual cut off number is usually in 216-219 range for Florida.