I don't understand how states representing the U dot and V dot are updated or predicted?

[Helaly96]

Hello, thank you so much for the library. I am implementing a variation of it and including other criteria to the states as well (depth of object )

i have a question tho, for the U dot and V dot , i don't understand how they are predicted. as they are not measured (so obv not corrected in update step) , and neither the State transition matrix nor the measurement matrix updates it by any means.