Don´t be confused by the decimal point.
On my a/c (l1011) we have (I)EPR guages.
I= Intergrated because we have LP air mixing with HP air at the engine exhaust.(Hp air is Ip air further compessed before anyone asks).
T/O power should be set before 80 kts after which the power will roll back due to intake ram px.
eg max t/o epr(isa day) .643= 1.643*intake pressure.
inflight t/o epr(go around power) .631 =1.631*intake pressure.
the 2 power settings are the same ie throttle setting and fuel flow. the speed is the only thing that changed.
if you were to set the former above 80 kts you would be overboosting the engine.
In the descent above 350 the min epr the fms will set is .122epr reduceing to .087epr below around 310 then .0 epr below around 280.
this is for bleed air management and sub idle spool speed at high level.
when the throttles are at idle in the descent the epr indicated varies with tas but is usualy between .01 and .04
When the thrust management system indicates an epr value it does not show a decimal point. ie 122, 087.
but one thing for sure, te pressure at the back is always more than the pressure at the front. if not then the fuel guages would be going up not down,(think about it)
nb this is my longest post in three years so I hope I´right.