What a missed notice really costs
A delay that was not your fault costs twice: the site stays open longer, so time-related preliminaries keep running, and without an extension of time the employer can deduct penalties for the same days.
A notice given in time protects both. The calculator puts the two side by side so the number is clear before the deadline passes.
Worked example
Time-related preliminaries are R365 000 a month, about R12 000 a calendar day. A 30-day delay costs R360 000 in preliminaries. With a penalty of R5 000 a day, another R150 000 is at risk without an extension of time: R510 000 in total.