The way to see this is not as a inlet/ engine/ reheat/ exhaust issue but as an overall powerplant concept.
The core engine (the turbine) is most efficent at lower airpseeds and the majority of the air coming into the powerplant goes thro the core and the combustion chambers to produce the thurst.
Here the intake+ turbine are needed to generate the thrust...
However as airpseed and altitude increase the 6 turbine bypass tubes open and begin to take a higher and higher percentage of airflow...it is this airflow which, being compressed by the intake geometry and then returned to the core flow upstream of the reheat ring which generates the majority of the thrust.. this is the ramjet part of the powerplant.. the core is still working conventionally but overall contributes much less. Effectively the intake and reheat are doing most of the work....and hte core very little.
So in effect the powerplant functions primarily as a conventional jet at lower speed ranges, and as a ramjet at higher speeds..by diverting airflow around the core turbine.
The reheat/ exhaust nozzle are the last piece of this puzzle...the reheat, used continuously in supersoinc flight acts as the sole burner for the bypassed air.. hence the ramjet tag..and the nozzle does it bit, regardless of what regime is dominant...
The reason why these figures can be calculated is that is relatively easy (!) to calculate the pressure increase as the airflow goes thro the intake and hence the thrust that generates..as well as calculate the fuel/ airflow through the engine.. again to work out how much thrust is there...the reheat/ exhaust is thus the remainder of the total...
What is interesting is that whilst the core only produces 25ish percent....the system is not self sustaining...the ramjet portion needs hte turbine section to be functioning..unlike a true ramjet which would not need the trubine once the right airspeed etc was attained.