Jinx Ultimate Projectile Speed

Hello, I want to know if there's exact/confirmed information concerning Jinx's Ultimate . I know that her Ult speed changes mid-flight and the wiki for her states that the rocket travels 1500 units in the first second and the rate increases to 2500/s after the first second, however it mentions that it needs to be tested. Is this information correct or is there any way to find out the accurate numbers from Riot?

Any help would be appreciated, thanks! :^)