I do recommend a specific gravity (of the Lye solution) of about 1.05 to 1.1 (using a hydrometer).
Here’s a good video on what a hydrometer is and how to use a hydrometer (need a test cylinder too)
You can get a good kit from Amazon. Be sure it is a hydrometer and not (or not only) an alcohol meter.
Or just mix 80 grams of lye in the first mix of solution. The solution does NOT need to be exact. In fact it’ll vary normally as the water leaves, the remaining solution becomes more concentrated.
We used to recommend more lye (like I previously recommended up to 150 grams), but we’ve found it leads to excessive internal lye crystallization that causes clouding if the sight tube and exacerbates any internal plugging (due to sludge formation or oil contamination turning to soap). The machine will work well with as little as 30 grams of lye in it.