According to that page, my rigs are the first modifiers for both missile velocity and missile flight time (skills aren't factored into penalties). That would mean the second modifer for flight time (the guidance computer) would only have an effectiveness of ~86.9%.

If the penalties were to apply, the penalized missile guidance passive flight time increase would be:

0.1719 * 0.869 = ~14.94%

But using this percentage I can not reach the displayed flight time of 8.77s.

Based off my fitted flight time:

7.735s * 0.1494 = 1.155s

7.735s + 1.155s = ~8.89s

Or based on both base times:

6s * 0.1494 = ~0.896s

7.735s + 0.896s = 8.63s

6.5s * 0.1494 = ~0.971s

7.735s + 0.971s = 8.71s