When reporting taxable income, we are supposed to set off losses against incomes first, and then report only the remaining income. So the capital gains to be reported here are those obtained after setting off (subtracting) both current-year losses and losses brought forward from previous years. Of these, since the brought-forward losses happened first, they have to be set off against incomes, first.
If you have STCL brought forward from previous years, and STCG in various quarters of the current year, then the amounts to be entered in these boxes will be zero till the first quarter in which there is a net profit (after offsetting previous and current-year losses).
In particular: if you have STCL brought forward from previous years, and your STCG in the current year is not sufficient to offset all of those losses, then all the four boxes will have zeroes in them.
The carrying-forward of remaining losses happens in a different schedule (CFL), and is not affected by what you enter in these boxes.