GMAT Critical Reasoning (CR) | Re: According to a research of 1000 individuals, 70% of the people who wer

In this question - this is what i did:
# of people who are part of GSP - x
70% lost avg. of 4 pounds in month = 0.7x
(question doesn't say anything about > 4 pounds but ideally i assume 50%) => 0.35x lost > 4 pounds in month

# of people who lost 4 pounds in month = y
80% lost avg. of 4 pounds in month = 0.8y
> 4 pounds => 0.4y

I am not able to figure out how can we say 0.4y > 0.35x?
We don't know what is the exact value of x and y. What am i missing, can someone please clarify?
Thanks
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