Note that color(red)(16) can and may be written as color(red)(+12 + 4)
So color(green)(-12)color(red)(+16) is the same as ubrace(color(green)(-12)color(red)(+12))color(red)(+4) color(white)("ddddddd.ddddddddddddddd") darr color(white)("ddddddddddd.dddddddd.ddd")0color(white)("dd..")+4