Cut off means the minimum marks required for a student in order to cross the threshold of passing the examination. Now the score you are mentioning about the Economics paper in IIT JAM is good score and its good for getting newer IIT's if you are an UNRESERVED Student. The rank you can expect may lie in between 340-600. The variation is dependent on the type of students attempted, but this is the past year trend wise analysis.

For more information regarding the IIT JAM examination you can visit the link below:

https://university.careers360.com/exams/jam

I hope this helps. Wish you a great eve!