trust me, its not that simple,
software has to be rewritten, then tested, then run in a test environment usually over a period of 12 cycles, (12 months) this has to be then evaluated, checked , double checked and then implemented, this takes about 2 to 3 maybe 4 months,
it used to be just 20% of the ceiling or interest paid whichever was lower, now its a few different rates.
but any trs due will be refunded, so if you are due more trs, at least it will mean lower repayments towards the end of the year.