@Ghang I believe that 偏差値70 would mean grades that are in the top 2% of students and the joke is she takes it to mean just scoring 70%s on her tests.
If you know stats, you can see the jdict definition for 偏差値 mentions a mean of 50 and standard deviation of 10, so 70 means two deviations above...
The comments from Nekomata should be here: https://mangadex.org/title/20792/nekomata/comments/
But it's actually showing the comments from a different series: https://mangadex.org/title/20871/the-jinx-s-lover/comments/
On each of those, if you check the URL the "view older posts" button takes...