as per my research calculation should like this "For QSB stock acquired before Feb. 17, 2009, 50% of the gain can be excluded.

For QSB stock acquired from Feb. 17, 2009, to Sept. 27, 2010, 75% of the gain can be excluded.

For QSB stock acquired after Sept. 27, 2010, 100% of the gain can be excluded." but instead calculating 60% https://www.investopedia.com/terms/q/qsbs-qualified-small-business-stock.asp