Not a 208 pilot, but been taking to one who is considerably experienced on type, and trolled his library for 208 info.
Beginning with serial number 372 (1044 for the B) Cessna fitted an Altair ETM which will record an exceedence if the engine is operated above the "maximum cruise power" as detailed in section 5. The ETM was fitted so as to make the engine eligible for a higher TBO. I guess the engineers must interrogate the ETM to determine what the TBO times for the various components may be.
That is not to say you can't exceed the max cruise power (but keeping within ITT, N1 limits), it's just that it will be logged and may impact the TBO.
The G1000 has a moving marker which will indicate the max cruise power applicable at the time.
Re horsepower. The first TQ red line is at 1865 and says "TO" next to it.
1865TQ X 1900RPM / 5252 = 675 horsepower
The second red line is the climb
1970TQ X 1800RPM / 5252 = 675 horsepower
Pull the RPM back while maintaining 1970TQ (assuming other limits are OK)
1970TQ X 1600RPM /5252 = 600 horsepower