RampUp and Rampdown Scenario

I would like to get a bit clarity on these two injection steps

  1. rampUsersPerSec(0) to(166) during(1200)

2)rampUsersPerSec(166) to(0) during(1200)

My question is,does the rampup happens starting with 0 per sec,1/sec,2/sec,3/sec and so on…till it reaches 166/sec during 1200 seconds or will it try to hit any value in between 0 to 166 in the given duration of 1200 seconds.Correct me if i am assuming anything wrong in this case.