Well, she was right to be concerned. I crunched the numbers with a couple of nifty formulae and I'm afraid anyone trying this challenge will be disappointed when at the end of the year, they find themselves with just £96.46. Not a small amount, I admit, but it's just a fraction of the sum people will be expecting.
I don't know if the original poster just got their maths a bit muddled, or if they're deliberately leading people astray. Either way, you can follow a similar pattern and end 2016 with £671.61 in loose change! If, instead of saving a daily sum relative to the week, you save a daily sum relative to the day you will save a lot more.
Let me explain that another way. On day one, you put a penny in your piggy bank. On day two, you put 2p away. On day 3, 3p etc. Even if you'd started on January 1st and did this every day until December 31st, the most you'd have to put away on a single day is £3.66 (it's a Leap Year, after all.)
I think putting away between 1p and £3.66 a day is still perfectly achievable and, unlike the other challenge, it will actually result in over £600 saved.
Now, if you want to save the full whack of £671.61 by the end of the year, you will need to "back date" your first deposit to account for the days missed. For instance, if you started tomorrow you'd need to start by putting away 55p, then continue as planned with 11p on January 11th, etc. Missing out ten days might not seem like a lot, but if you miss ten days at the beginning of the year, you'll also miss the ten days at the end. These are the days that you're saving the largest deposits, and while they're still only £3.66 at most, those ten days combined are worth almost £40! So if you take the hit and put away your "catch up money" now you'll end up with more in the long run.
I know this all might seem a bit confusing and bonkers, but I promise you the maths works out. You really can save over £650 in a year by saving less than a fiver a day.
What would you do with £671.61? I'm planning a holiday with the girls...