unit of vel in m2/day

why is unit of groundwater vel given in m2/day? in 2d flow module?
Also what is the significance of the arrow given at the end of all flow properties legands, like storativity,porosity etc?

In 2D confined models, a depth-integrated Darcy velocity is given as FEFLOW does not have any information about aquifer thickness (transmissivity is used as the material property).