SubsuperscriptBoxOptions -> {opt_1 -> val_1, opt_2 -> val_2, ...} is an option for selections that specifies settings for SubsuperscriptBox objects.
Subsuperscript[x, y, z] is an object that formats as x_y^z.
x -= dx subtracts dx from x and returns the new value of x.
x - y is equivalent to x + (-1*y).
SucceedsEqual[x, y, ...] displays as x \[SucceedsEqual] y \[SucceedsEqual] ....
Succeeds[x, y, ...] displays as x \[Succeeds] y \[Succeeds] ....
SucceedsSlantEqual[x, y, ...] displays as x \[SucceedsSlantEqual] y \[SucceedsSlantEqual] ....
SucceedsTilde[x, y, ...] displays as x \[SucceedsTilde] y \[SucceedsTilde] ....
SuchThat[x, y] displays as x \[SuchThat] y.
SumConvergence[f, n] gives conditions for the sum \[Sum]_n^\[Infinity] f to be convergent.SumConvergence[f, {n_1, n_2, ...}] gives conditions for the multiple sum \[Sum]_n ...