the unit translation in multiphase flows

Hello dear friends,
I am simulating a bubble rising in the water, and now i am confused by a question about the unit transformation.
From the parameters that i set, i can get the accelerated speed g= 6.2e-7 in the LB unit. So according the real value of g(g = 9.8m/s^2) in the physical unit, and the value of the sound speed in water (about 1400m/s), can i get the value of dt and dx ? As we all know, the square of the LB sound speed is 1/3.
In my opinion, because we have known the value of g and sound speed in the physical unit, and have know the value of them in the LB unit, we can get the value of dt and dx. But the value i get is:
dt = 1.5341e-4s, dx = 0.372m.
it seems not right, expecially the value of dx, it seems too big. Could anyone help me ? Tell me what’s mistake have i made.
Any reply is appreciate, thanks.