Ive been having problems with my storage lastly and I went and looked at it and it says that 34Gb are left but when i did some maths all of it it added up to 71.12Gb left and I would like to know why.
MacBook Air
I realize none of the following directly answers your question "why" but the largest single category in your screenshot appears to be System Data.
Refer to See used and available storage space on your Mac - Apple Support. Pay particular attention to what it says about it: "You can't manage the contents of this category." It varies all the time, which at least partially explains your observations.
You may find neuroanatomist's User Tip helpful: What is "Other" storage on a Mac, and how can I clean it out? - Apple Community.
If you want a real trip down the "storage" rabbit hole, read this discussion.
I realize none of the following directly answers your question "why" but the largest single category in your screenshot appears to be System Data.
Refer to See used and available storage space on your Mac - Apple Support. Pay particular attention to what it says about it: "You can't manage the contents of this category." It varies all the time, which at least partially explains your observations.
You may find neuroanatomist's User Tip helpful: What is "Other" storage on a Mac, and how can I clean it out? - Apple Community.
If you want a real trip down the "storage" rabbit hole, read this discussion.
You can’t add it up yourself. The file system is too complex and too much of it is hidden. If you are only 40 GB off, you’re doing better than many people. It isn’t unusual for people to have hundreds of GB less than they think.
Now I only have 4.28 GB left
Storage is telling me the wrong thing.
