Capabilities not saving

[Make custom fireball]

Hello this is my first time working with capabilities and I'm still a bit confused on things but when i leave the world and log back in my capability is set back to 0.

I made it so whenever I pressed a button in a gui it sends a packet to the server and increases by 1 https://github.com/Applhau/JujutsuKaisenMod/blob/main/main/java/net/Applhau/jjkmod/client/gui/StatGuiScreen.java (line 91)
packet: https://github.com/Applhau/JujutsuKaisenMod/blob/main/main/java/net/Applhau/jjkmod/network/message/IncreaseHealth.java

sadly it never saves so it just resets after i relog
this is where i put all my capability stuffhttps://github.com/Applhau/JujutsuKaisenMod/tree/main/main/java/net/Applhau/jjkmod/util/data

any help on making the system better will be appreciated but im mainly focused on having the capability save.