Update () and Fixedupdate ()

Http://www.cnblogs.com/guanjie20/p/3549392.html

update is called each time a new frame is rendered . and Fixedupdate will be called at every fixed time interval ,

So what if the time interval between update and fixedupdate is the same? The answer is not necessarily, because the update is affected by the current rendered object, more precisely the number of triangles, sometimes fast and sometimes slow, the frame rate changes, and the time interval at which the update is called changes. But

Fixedupdate is not subject to frame rate changes, it is called at a fixed time interval, then how to set this time interval? Edit->project Setting->time below the fixed timestep.

Update () and Fixedupdate ()