trouble understanding init_domainfill.f90

[nehstand]

Hello,

I am trying to understand the initialization of particles in init_domainfill.f90. I'm having trouble understanding the following lines (54 to 57) :

nx_we(1)=max(int(xpoint1(1)),0)
nx_we(2)=min((int(xpoint2(1))+1),nxmin1)
ny_sn(1)=max(int(ypoint1(1)),0)
ny_sn(2)=min((int(ypoint2(1))+1),nymin1)

As far as I understand nx_we, ny_sn are the grid indices for western, eastern, southern and northern boundary of the release domain.

My question is the following : what happens if one of the longitudes and/or latitudes bounding the domain are negative? That is if one of xpoint1, xpoint2, ypoint1, ypoint2 < 0 ?
It seems to me that these code lines restrict our domain to positive values. However, I know from experience, when using Flexpart, that there is no such restriction.

Thank you in advance!