"If" and "Weight Sum" search parameter

Does anyone know how the "IF" and "Weight Sum" search parameter work on the trade site?

Is IF, like using OR in mathematical term... This "OR" This?

What is the weighted sum equal to for "Weight Sum" parameter? 1?
like if I had 10 mods in the search pool, should the weighted sum up to a total of 1 with the most wanted affix having the majority of the fraction?

And if I am using these two in combination to live search some uniques early league for my build, how would I add any number of a unique specific mod affix to have an "IF" parameter that the explicit should ATLEAST have so and so value?