I scan at https://web.dev/measure/ for 'https://x.bapha.be' and the report at https://lighthouse-dot-webdotdevsite.appspot.com//lh/html?url=https%3A%2F%2Fx.bapha.be says:

• Eliminate render-blocking resources Potential savings of 30 ms
Resources are blocking the first paint of your page. Consider delivering critical JS/CSS inline and deferring all non-critical JS/styles. Learn more.

URL | Transfer Size | Potential Savings
-- | -- | --
/j/e-385d523a.css(x.bapha.be) | 12.6 KB | 180 ms

So for the CSS URL the potential savings are 180ms, but the whole potential saving on this criterion (for all URLs) is 30ms.

It is utterly unclear, how these 30ms == 180ms are calculated. If the calculations are correct, please update the picture at the top of https://web.dev/render-blocking-resources/?utm_source=lighthouse&utm_medium=lr to contain a sum, that is less than its addends.