Because the top 60 winners are fixed, but the winning grades have changed, the total scores of these 60 winners remain unchanged.

Assuming that the original average scores of the first prize, the second prize and the third prize are x, y, z Y and z respectively, the adjusted average scores of the first prize, the second prize and the third prize are X-3, Y-2 and Z- 1 respectively.

According to the topic, we know that y=z+7.

According to the total score of the top 60 unchanged, we get:

5x+ 15y+40z = 10(x-3)+20(y-2)+30(z- 1)

Upon completion, you will receive:

x+y=20+2z

Replace z with z=y-7.

There is x=y+6.

The adjusted first prize and second prize are X-3 and Y-2 respectively.

Then it is (x-3)-(y-2) = x-y-1= y+6-y-1= 5.

The final answer is 5.