I'm not sure the definition explains the usage in this case.
it makes sense to me; it's somewhat out of the ordinary to have bought a sound blaster recently, thus the author is verifying that that is indeed what they meant to write.
Makes sense with the context, but at first I, too, was confused. And it's not the first time I see such usage of "sic!" as confusing. <joke>Perhaps it should be "(sic! sic!)" in less obvious contexts to clarify that the first "sic!" is actually intended there.</joke>
Buying a SoundBlaster 16 in 2023 is well past it's prime. He's clarifying that this isn't a story about months after in 1993 era, but a story in the present day.