After browsing through the long list of bonuses, a memory struck through his mind like a falling meteor - the highly sought after 'golden shell pocket-watch' he got from the terminator world! Although it only added 1 physique, on hindsight now; Sheyan could tell his customers were targeting those few private bonuses when an accessory is upgraded!
More critically, the amount needed to upgrade an equipment differs. Sheyan previously already noticed that the utility points and potential points needed to upgrade a silver storyline weapon 'Monstrous fighting spirit' was terribly frightening. It required 2500 utility and 1 potential point. On the contrary, that golden pocketwatch only required 500 utility points.
His customers were all eyeing to acquire the watch to upgrade it to +4. Even if they didn't receive the satisfactory bonus, they could roughly pay to demote it to +3 before trying again. Thus, it was a lower risk investment to draw out that formidable miracle private bonus.