Could someone please help me understand?

I was going through the coin explorer in Washington quarters looking at members pictures at the bottom of the page.I came across the 1976D,the two pictures at the bottom of the page were both MS67 but they had different scores.It appears that in the 65 to 98 set it scores 348 points but in the quarter dollar type set(inc 20 c) the same coin only scores 304 points.I thought points were given to a coin regardless of what set it is in.could someone explain why a coin would go up or down in points depending on what set it is in??

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