How it works
The calculator runs two balances side by side. Each period it moves your transfer amount out of the source and into the destination, then lets each side earn its own assumed return on whatever it holds.
The source therefore behaves exactly like an SWP being drawn down, and the destination exactly like a SIP being built up. Both use the same engines and period conventions as those calculators, so the numbers here are consistent with what you would get running them separately.
More detail
For context the calculator also reports what the whole corpus would be worth had it been switched across on day one. That figure is almost always higher when the destination's assumed return exceeds the source's — which is arithmetic, not an argument.
Once the source runs dry the transfers stop, and the final transfer is whatever was left rather than the full amount.
The source side of an STP is drawn down the same way an SWP is, so the SWP calculator.
To model the single-switch case on its own, use the lumpsum calculator.