All pieces of gear have caps in terms of their stats. With regards to the gear you’ve listed, the stats are listed as follows (HQ gear values are listed in parentheses; max values allowed for each stat per piece of gear are listed after the given values):
Gaganaskin Gloves of Gathering:
—GP: 4; max: 5
—Gathering: 97 (110); max: 129
—Perception: 0; max: 9
A Perception IV Materia offers +6 Perception, and a Perception II offers +4. Since you can only meld up to 9 points of Perception, the gear will be unable to fully accept any materia in the second slot except for Perception I materia, which offers +3 Perception. The Perception IV and II will cap the gear at over +9 Perception, resulting in you losing points (you will lose 1 point with the Perception II, since 6 + 4 = 10). Trying to meld +12 Perception (i.e., two Perception IVs) will result in the loss of 3 stat points (6 + 6 = 12), hence why you were receiving the message saying that the full value of the materia cannot be accepted into the gear.
Bloodhempen Trousers of Gathering (this is not a naming bug, by the way—this piece of gear is a WVR recipe, where as the Gaganaskin pieces are all LTW recipes; not all pieces in a gear set always share the same name, and it’s fairly common for a couple pieces to be from different crafters):
—GP: 0; max: 5
—Gathering: 65 (73); max: 86
—Perception: 6 (7); max: 9
With this piece of gear, you will be unable to attach any Perception materia without losing at least some of the point value of the materia, unless the piece of gear is NQ, then you can meld a Perception I materia without losing any points off the materia. However, if the gear is HQ, you will still lose at least 1 point of Perception (more if you’re attempting to meld anything higher than a Perception I), since the gear caps out at +9 Perception (Perception I materia offers +3 Perception). I’m guessing you were attempting to meld Perception IV and then Perception II again; with both materia, since their values are higher than what the gear can accept, you will lose out on some of the stat points.
As for the numbers you see at the bottom next to the different crafter icons, these are the minimum level required to perform self repairs on the gear. So, for the pants, you would need a Level 53 WVR in order to repair your own gear. For the other pieces, you need a Level 54 LTW.