No increaes functions differently from other modules, see these sections on page 66.
Add a Matrix Attribute: You can add a rating that a device doesn’t have, specifically Attack or Sleaze. When you perform this mod, the rating starts at 1. You can’t add a Matrix attribute to a device that already has that attribute. Remember that all devices have Data Processing and Firewall, even if that information is not listed in their gear entry. The Increase a Matrix Attribute modification can later be added to this modification. The number of parts packs needed for this modification equals the (Device Rating x 2) of the object being modified.
So unlike the usual limits you can add an attribute and then increase it as for increase attribute its hard to say whether its stackable or one off. Personally I read it as having a limit of one point but this comes back to my current opinion a lot of these new options are actually fairly useless in practice.