So I'm using the following formula to calculate my anticipated FIRE date. If I increase the contributions by $500/mo, it changes my FIRE data (in excel) by about 8 months. If I add a reoccurring $500 savings increase in the application, it reduces my time to FIRE by over 3 years. Is this a bug in the application, my excel formula or a difference in how you are calculating the average return? I'm using a modest 6%.

=TODAY() +NPER(6%/12,-35000/12, -L10, 30000*25)/12*365.25

Edit: I should also note, that if I take my $35K annual contributions and increase it to $41K in the baseline section of the application, it reduces my time to FIRE by only 8 months (As my excel calculation does), not the 3 years which the hypothetical contributions would.

Edit 2: By removing the "What-If: Adjust 'what-if' reoccurring savings/spending with inflation" checkbox, the new calculation drops to 9 months. Interesting.