From a french forum :Yes we can assume just like you assumed/lied the F-35 "supercruised" 150 miles in "slight decline." Since Duhssault doesn't even give an estimation of range like the US does for F-35 and F-22 it leads me to suspect the Rafail supercruise is for such a short period of time that they don't dare to even give an estimation. If the Rafail can go over mach1+ for 20-30 miles without afterburner than yeah it technically supercruised and Duhssault can claim the plane can SP. That simple.
F-35's F135 was not built to supercruise it has a time-at-temperature limitation on its turbine that restricts it from continuous supercruise operation. I can tell you this F-35 SP goes much farther than Rafail and its what... 13-14k pounds of fuel which includes the1250 liter center tank...unless you got any sources from French air force or Dassault saying otherwise?
Seems you're sorta in a catch 22, eh? Rafail with a 1250 liter center tank carries waay less fuel than F-35 and the F-35 can "SP" for 150 miles which means Rafail.... Get where I'm going?
The super-cruise configuration is Mach 1.4 with 6 missiles or 4 missiles and a 1200L tank (source Dassault Le Bourget 2011 : http://rafalefan.e-monsite.com/medias/files/fiche-rafale-le-bourget-2011.jpg see my picture below taken on Le Bourget Dassault stand).
We can take the data from the F404 engine, older than M88 but in the same class. At Mach 1.2 and 30,000 feet : Full throttle dry: 5,480 pounds or 2,485kgf
Consumption: 5.650 lbs / hour or 2.560kg / hour
Specific consumption ~ 1.03 ( https://www.nasa.gov/centers/dryden/pdf/88166main_H-1556.pdf )
The M88 pushes a little more (+ 5%?) but has a slightly better specific consumption (-5%?), So the full dry gas consumption must be very close. Either for the Rafale 2x 2,560kg / hr. Let say 5,100kg / hour.
It's for 30,000 feet. At optimum altitude (~ 37,000-40,000 feet), the Rafale’s full dry gas consumption will be reduced by around 15-20%, or ~ 4,100-4,300kg / hr.
The fuel internal capacity of Rafale is 4700kg. Add 1000kg for the centerline tank.
The bird need to reach this altitude. Let's say it uses the 1000kg of the external tank. This gives M1.2-1.4 more than 1 hour of autonomy or more than 700-800 nautical miles in supercruise.