Yes thank you that's what I meant. It enters the circulatory system for her to use, but still didn't increase her base amount, which is what nature chakra mixes with. Think of it this way, if somehow she could use the seal to use sage mode; with sage mode, you take in nature chakra from the world. You need to mold/control this nature chakra to balance with your own spiritual and physical chakra, so all the are in unison together. Now that is extremely hard as it is, but now add a fourth chakra, that is coming from her seal, she would need to mold and convert/control four different chakras together. Which is probably impossible. That's still only if she could somehow use the seal, but I dint think she can. The bathtub analogy was spot on. Oh and yes, the point of the seal is so you don't have to use your own chakra/stamina for big jutsus...and it is the only way katsuyu can heal other people also, katsuyu draws chakra from the seal. Yes katsuyu can heal with her own chakra, but not to the extent that she can with drawing from the seal.