Gemini's predicted full marathon time based on my estimated 5k TT of 20 minutes lol

There are many factors to consider like body weight, long-distance training, and mileage, but based on last year, it was accurate lol. I finished in 4 hours 11 minutes. Can I actually expect a sub-4 at the All-Jeju Marathon? lol (And if I fail, I can just try again at the Seoul Marathon lol)