Two things.
1/
The "600+ score received" part is ambiguous; it's not clear what those percentages represent.
Do they mean...
... Of students who studied for this long, here's the % scoring over 600?
or...
... Of students scoring 600+, here are the %'s who studied for X amount of time?
Those would be very different indeed. If it's the latter, then it doesn't mean anything at all, other than that the # of people studying for longer is probably greater than the # of people studying for less time.
2/
"600 is minimum GMAT score [sic] for top ranked [sic] business school"
--> False. I've had tutoring students who were admitted to Stanford GSB and HBS, among others, with GMAT scores below 600. (Of course, there were other outstanding features of their applications.)
Also, a quick glance at the schools' pages will show GMAT ranges starting below 600.
Ron has been teaching various standardized tests for 20 years.
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