Stress Track Parenthesis

[gpasha]

I have read in one post that the stress track boxes in parenthesis indicate conditional boxes. Can someone explain what that means and when a creatures would have the conditional boxes available and when not?

[bibliophile20]

Toughness powers grant those "bonus" stress boxes; if the Toughness' Catch is applied, then those boxes don't apply--and if a stress larger than the now-reduced stress track is applied, the character is in danger of being taken out.  

EDIT:
Example: A Malk (a fey) has four stress boxes, two normal, two from Toughness.  Shooting a Malk with a lead bullet (Weapon:2) will probably just annoy it, with the second of four stress boxes full.  Hitting it with an iron crowbar (Weapon:2) will fulfill the Catch, bypass the Toughness and negating those additional boxes, and seriously hurting it, filling the second of two stress boxes. 

[gpasha]

Thanks, that really clears it up. I couldn't find this information in the rules. Nice example!