For the answer to the question above, It means Brian is switching from saving $25 dollars a week to $35 dollars a week. Because every week Brian will add $25 to his savings account (In week 1, Brian adds $25. In week 2 Brian adds $50. And so on). So to change from 25 to 35 would mean that Brian is saving more money every week ($10 to be exact).
And if you're curious, $350 stands for the amount of money Brian has initially (because at 0 weeks, Brian has $350 in his savings account).
I hope this helps
