I recently came across the withdrawal rates chart from Portfolio Charts which gives an SWR and PWR for a targeted mix of assets (https://portfoliocharts.com/portfolio/withdrawal-rates/). When I put in my current asset mix of 70% S&P 500 and 30% Intermediate Term Bonds I see those rates for a 40Y retirement being 3.8% and 3.2% respectively.
My current retirement assets are 2.2M across taxable and tax advantaged accounts. We dont have any heirs so plan on consuming 100% of these accounts during retirement and have no need to leave a bequest to anyone. Given that fact, and assuming that a 3.5% withdrawal rate would be fairly bulletproof moving forward, I initially came up with an annual spending amount of ~77K (2.2M*.035). Is that the right way to determine this type of number? The reason I ask is when I use the PWR method above and do 2.2M*1.032/40 I get a much lower number of 57K/yr.
I've now worked myself into mental knots trying to figure out which number is the correct one to use for planning but I cant figure it out

Any help educating me on what I am sure is basic math would be most appreciated.