Sunday's race was set to be 24 laps but will now run for 19 after a report from Pirelli recommended that the distance was shortened due to the level of tyre wear experienced in Saturday's sprint race.
Motorsport.com understands that Pirelli brought a softer tyre to the race upon request to have a more aggressive compound.
At Silverstone last weekend, the series used the hard compound.
Some drivers complained of excessive wear on the medium compound, with second-place finisher Nikita Bedrin saying "mid-race the tyres started to die."
Race winner Gabriele Mini said: "At the end we were running more or less five or six seconds slower than the beginning, so you can imagine degradation was really high and it was all about just driving until the end."
On Saturday evening, it was revealed that the race would be shortened to either a total of 19 laps or 45 minutes plus one lap.
The stewards said: "The Stewards after receiving a report from the official tyre supplier recommending that the FIA Formula 3 Race 2 be limited to no more than 19 laps due to a level of wear experienced during Race 1.
"Having considered the matter extensively and after consultation with the Race Director and Technical Delegate, decide to modify the length of Race 2 to 19 laps for safety reasons, in accordance with Article 5.3 of the FIA F3 Sporting Regulations and under the power granted to them under Articles 11.9.3. b) and 11.9.3. o) of the 2023 FIA International Sporting Code.
"The Stewards request the Event promoter to take note of the new number of laps and to issue a new timetable."
Several drivers received post-race penalties after Saturday's sprint race, with all three Van Amersfoort Racing runners penalised after the team continued to work on the tyres beyond the specified time limit for them to be returned to parc ferme.
Caio Collet, Tommy Smith and Rafael Villagomez will serve five-place grid penalties in the next race in which they compete.
Collet has also been handed a separate 10-second time penalty for causing a collision after making contact with Rodin Carlin's Ido Cohen, dropping him from 14th to 23rd in the sprint race classification.
Woohyun Shin, making his F3 debut for PHM Racing by Charouz, was handed a five-second penalty for exceeding track limits four times during the race but remains 26th in the classification.
Hitech driver Luke Browning was also handed a five-second time penalty for leaving the track and rejoining after Turn 7 and gaining an advantage. He passed Oliver Gray (Rodin Carlin) in the process and failed to hand the place back. It drops him from 11th to 16th in the final classification.
Nikola Tsolov was handed a five-second time penalty for causing a collision after making contact with Pepe Marti (Campos Racing).
The ART Grand Prix driver made contact with Marti in the battle for eighth, spinning him after making contact from behind.
With the Bulgarian driver failing to make the chequered flag, his five-second time penalty is converted into a three-place grid drop for the next race he participates in.
