 size is set by the &quot;timestep&quot; command
when running rRESPA, all input commands that specify numbers of timesteps
  (e.g. run, thermo flag, restart, etc) refer to the outermost loop
  of long-range timestepping
the only exception to this rule is the &quot;neighbor&quot; command, where the timestep
  parameters refer to the short-range (nonbond) timestepping
when using constraints (via the &quot;fix style&quot; and &quot;assign fix&quot; commands)
  with rRESPA, the setforce and aveforce constraints