Well, first of all, let's not make something complicated ... for which we're missing an important component anyway ... out of something simple. There's more to "velocity" than 'meters per second'. So let's just call that what it is: " Speed ".
Here's what you've told us:
-- Something is moving along a ruler or meter stick.
-- At every instant from time=0 to time=5, its speed was constant at 4 m/s.
-- At time=0, it was located at 6m .
We can calculate:
-- Moving steadily at 4 m/s for 5 seconds, it moved (4 x 5) = 20 meters.
-- If it was located at 6m when time=0, then at time=6, it had advanced
to (6 + 20) = 26 meters.
