Position of runoff

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Dear CROCO members,
I am trying to add some rivers into a tropical Atlantic configuration. I downloaded the croco_tools-master on 1/10/2021 (https://gitlab.inria.fr/croco-ocean/c...)
I read the documentation and used the make_runoff.m script to generate a climatological flow/salinity input file. I understood that the position indexes (Isrc and Jsrc) are specified in the u/v grid for horizontal/meridional flow, respectively. The outputs of locate_runoff.m, I2(:) and J2(:), are indeed the coastline positions in u or v grids, depending on the direction (E->W, W->E, S->N, N->S) of the flow.
These positions are ready to be written in the croco_runoff.nc, but not yet used. As far as I unserstood, I have to copy the text output at the end of the execution of make_runoff in my croco.in.
-----> I do not understand why, when listing the position in make_runoff.m, these indices are modified (I2-1 for meridional flow and J2-1 for zonal flow):
if dir(k,1) == 1 %%flow meridien
disp([' ',num2str(I2(k)-1),' ',num2str(J2(k)),...
' ',num2str(dir(k,1)),' ',num2str(dir(k,2)),' 30T ',...
num2str(T),' ',num2str(S)])
elseif dir(k,1) == 0 %flow zonal
disp([' ',num2str(I2(k)),' ',num2str(J2(k)-1),...
' ',num2str(dir(k,1)),' ',num2str(dir(k,2)),' 30T ',...
num2str(T),' ',num2str(S)])
end

Note that I slightly modified the figures generated by make_runoff.
1) In the big map with all the rivers, pcolor does not plot the land/sea mask cell centered around the lon/lat position of each cell. I suggest shifting the axes by dl/2 (just for the drawing): m_pcolor(lon-dl/2,lat-dl/2,mask)
2) When continuing plotting the big map, the adjusted position of the rivers, I2 and J2, should be plotted using the lonu/latu or lonv/latv grids (and not the rho grid), such that:
for k0=1:number_rivertoprocess
k=rivertoprocess(k0);
if dir(k,1)==0 %zonal flow (u-grid)
lon_src=lonu(J2(k),I2(k));
lat_src=latu(J2(k),I2(k));
else
lon_src=lonv(J2(k),I2(k));
lat_src=latv(J2(k),I2(k));

end
[px,py]=m_ll2xy(lon_src,lat_src);
if dir(k,1)==0 & dir(k,2)==1
h3=plot(px,py,'k>');
elseif dir(k,1)==0 & dir(k,2)==-1
h3=plot(px,py,'k<');
elseif dir(k,1)==1 & dir(k,2)==1
h3=plot(px,py,'k^');
elseif dir(k,1)==1 & dir(k,2)==-1
h3=plot(px,py,'kv');
end
set(h3,'Clipping','off')
end

Thanks in advance for your answer
Serena