rl=0 delta_t=4.0 timefac=1
rl=1 delta_t=2.0 timefac=2
rl=2 delta_t=1.0 timefac=4

it == 0:
rl=0 t_of_level=0.0
rl=1 t_of_level=0.0
rl=2 t_of_level=0.0

it == 1:
rl=0 t_of_level=4.0
rl=1 t_of_level=2.0
rl=2 t_of_level=1.0

it == 2:
rl=2 t_of_level=2.0

it == 3:
rl=1 t_of_level=4.0
rl=2 t_of_level=3.0

it == 4:
rl=2 t_of_level=4.0

if wanting to compute every Delta_t = 4.0 which is every 4 iterations, need to
evaluate at:

it = 0 for rl=0,1,2
and
it = 1 for rl=0
it = 3 for rl=1
it = 4 for rl=2