Let me first say I know (or think I know) how this rule is supposed to work, and will assume you do as well. But let me walk you down a path of reading and logic that shows how the text is confusing and should probably be changed.
OK, first let us look at the rules for equipment use:
Source Player Core pg. 235 "Equipment"
"Some abilities require you to wield an item, typically a weapon. You’re wielding an item any time you’re holding it in the number of hands needed to use it effectively. When wielding an item, you’re not just carrying it around—you’re ready to use it. Other abilities might require you to be wearing the item, holding it, or simply to have it."
OK cool, so if you hold and item in your hand(s), you are wielding it. There's a few exceptions (say if it needs two hands and you use one) but they aren't relevant to this discussion.
Now let us look at the rules for 4/6 hands from the ancestries that have them:
Source Player Core pg. 54 "Kasatha"
"You have four arms, which allows you to wield and hold up to four hands' worth of weapons and equipment. At any time, one pair of hands is designated as your active hands. You can change this designation from one pair of hands to another by taking the Switch Hands action action, which is a single action. You can wield items only with your active hands."
Source Player Core pg. 70 "Skittermander"
"You have six arms, which allows you to wield and hold up to six hands' worth of weapons and equipment. At any time, one pair of hands is designated as your active hands. You can change this designation from one pair of hands to another by taking the Switch Hands action, which is a single action. You can wield items only with your active hands."
OK, so I'm playing a skittermander and have a big gun in my active hands. I want to have a med patch in one of my other hands... but you are "wielding an item any time you’re holding it in the number of hands needed to use it effectively", so if I hold that med patch in any hand, I'm wielding it. The rules above say I can wield items only with my active hands. So I guess I can't hold that med patch in any non-active hand, ever....
Clearly this conclusion contradicts the intent, but it follows from the text because the meaning of "can wield items only with your active hands" is ambiguous. Does it mean that I can't do things that would result in wielding? To me that is the logical conclusion, but it clearly (or maybe not so clearly if that is the only source you have) is also NOT what the game intends.
I suggest these sections be changed as follows:
Source Player Core pg. 235 "Equipment"
"Some abilities require you to wield an item, typically a weapon. You’re wielding an item any time you’re holding it in the number of hands needed to use it effectively and those hands are your active hands. When wielding an item, you’re not just carrying it around—you’re ready to use it. Other abilities might require you to be wearing the item, holding it, or simply to have it."
Source Player Core pg. 54 "Kasatha"
"You have four arms, which allows you to wield and hold up to four hands' worth of weapons and equipment. At any time, one pair of hands is designated as your active hands. You can change this designation from one pair of hands to another by taking the Switch Hands action action, which is a single action. You wield items only with your active hands."
Source Player Core pg. 70 "Skittermander"
"You have six arms, which allows you to wield and hold up to six hands' worth of weapons and equipment. At any time, one pair of hands is designated as your active hands. You can change this designation from one pair of hands to another by taking the Switch Hands action, which is a single action. You wield items only with your active hands."