"MacBook Air M4: Battery, storage, and Bluetooth issues: hey there, > How much hours of battery backup are you getting for MacBook Air M4 512gb?? I am getting around 8 hours, which is really far away from what is promised by Apple.[...]"
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How Much Free Space to Use:
I recommend using up no more than 60% storage, leaving it 40% full for activities and other data creations(i.e. documents). So, all is normal and feasible.
Q1. "macOS is taking 22.77GB"
A1. Mac has its own storage on the hard drive. So, all that is created proceed from there, out of the box.
Q2. "System Data 34.57GB"
A2. About System Data on a Mac and how to Clear it: This is temporary files (mostly caches), which gathers over time. As apps are used, caches are created for the remembrance of App usage, so that they reply a a faster rate, and operate more effectively. As for instructions on how to clear it, Use my User Tip: How to Use Finder to Clear “System Data" on a Mac- User Tip
Q3. "I am unable to connect to a bluetooth mouse of another brand. like, it is not even discoverable by my MacBook. Thanks in advance :)"
A3. Research the compatibly of this mouse. Also, be certain it is not pairs to any other device. Also, reset the Bluetooth Module through Terminal. Use this Command: sudo pkill bluetoothd. See my User Tip: Use "Reset the Bluetooth module" to Fix Constant Bluetooth Disconnections - User Tip