holy,that’s 36% increased str

Afaik yes. Other commenter explained the math behind my choice. It’s hard to know if the math is mathing correctly in the code, but it should, as it works that way since the launch of the game.

Quality is a 1.2 multiplier. By default, quality rounds down (so 3% * 1.2 = 3.6%, but rounds down to 3%). But corruption applies after the quality using the non-rounded value, so corruption occurs on top of the 3.6, not the 3, and corruption rounds nearest, not down. So as long as you don’t roll an undercut (below 0.97), you get the increase. There is a 1-in-4 chance of rolling “changes modifiers’ values of the unique” when using a vaal orb, and after rolling a ‘changes modifiers’, you have ~50% chance of rolling above 1 multiplier and ~50% below 1 multiplier. OP’s result (1 positive outcome out of 8) is ok with the expected value. In terms of the fire increase, the chance is smaller, OP just got lucky in that part; this comment is focusing on the STR only (answer to the ‘quality’ part)

If he didn’t have the quality, to get 4% str he would need to roll 3.5+ on the STR value that was base 3, requiring at least a 1.17 multiplier (max is 1.22, minimum is 0.78; this cannot have more than 2 decimal places so this rolls in increases of 0.01), which is a 13.33% chance WHEN it rolls “changes modifiers’ values”, which again is 1-in-4. So total chance for 4% str would have been 13.33%/4 = ~3.33% chance of success, or 1-in-30