Some item mods, such as “Squire’s” on weapons and “Beetle’s” on armour-based body armours, can give the appearance of actually being two mods. These are hybrid mods, and are actually single mods that grant two stats at lower values. That means you may still be able to craft an extra mod onto that item! If you’re unsure if you have room on an item or not, try putting it in a Master’s crafting bench.