Another interpretation of "after the seven days" (Genesis 7:10): that during those seven days the Holy One, blessed be He, gave them a foretaste of the World to Come, so that they would know how much goodness they had withheld from themselves.
A Taste of the World to Come Before the Flood
Yalkut Shimoni on Torah 56:4
דָּבָר אַחֵר, לְשִׁבְעַת הַיָּמִים, שְׁהִטְעִימָן הַקָּדוֹשׁ בָּרוּךְ הוּא מֵעֵין הָעוֹלָם הַבָּא, לֵידַע כַּמָּה טוֹבָה מָנְעוּ מֵהֶן.