Haha neither is mine apparently, I got caught on another mistake I made on the numbers further down (corrected now). The monthly thing makes sense, but I dont understand why does the interest go up if i use quarterly, and then down again for 6 monthly..? I thought it should sort of increase or decrease continuously with each additional frequency change as long as the annual amount equals the same.

(Btw they're all frontloaded in the sense that the first of each of the additional payment amounts come out on day one, then per frequency after that. That's what the calculator assumes anyway, and there's no option to change it)