Yes.. correct.
The first
{d="arc_c",q=4,r=10,degs=90},
is the top left corner of that box.
Also
subtab={
{d="start",x=5.5,y=10.5},
{d="arc_c",q=4,r=10,degs=90},
{d="rline",x=200,y=0},
{d="arc_c",q=1,r=10,degs=90},
{d="rline",x=0,y=125},
{d="arc_c",q=2,r=10,degs=90},
{d="rline",x=-200,y=0},
{d="arc_c",q=3,r=10,degs=90},
}
grec({g=5,gan=65,x=5,y=10,w=200,h=125,grad={{c=0x000000,a=1,p=0},{c=0x000000,a=1,p=1}},lw=1,sub=1,db=0,subtab=subtab})
This is the base solid background and the following
subtab={
{d="start",x=5,y=10},
{d="arc_c",q=4,r=10,degs=90},
{d="rline",x=200,y=0},
{d="arc_c",q=1,r=10,degs=90},
{d="rline",x=0,y=125},
{d="arc_c",q=2,r=10,degs=90},
{d="rline",x=-200,y=0},
{d="arc_c",q=3,r=10,degs=90},
}
grec({g=5,gan=80,x=5,y=10,w=200,h=125,grad={{c=0x000000,a=0.35,p=0.0},{c=0xffffff,a=0.35,p=0.71},{c=0xffffff,a=0.35,p=0.73},{c=0xffffff,a=0.35,p=0.75},{c=0x000000,a=0.0,p=1}},lw=1,sub=1,db=0,subtab=subtab})
is the gradient overlay.
The bargraph.lua explains the different g=(gradients) you can use.