Different directions used for Hydrodynamic pressure calculation and Sea definition.

In quay.cif file in the sample folder, it is noticed that hydrodynamic pressure is calculated for 90 degree but sea is defined for -90 degree. What is the main reason for this opposite setting?

$********************************************* Frequency Domain
$
&parameter -m_distance 10
hydrodynamics
g_pressure barge -heading 90
end
$
$********************************************* define environment
$
&ENV TEST -sea issc -90 5 7.5 -TIME 100 1
&STATUS F_CONNECT
&STATUS Force
&equi -omega .4
$