The battery icon on the radio is that of the blue-tooth phone it is paired with, not the EV battery.
LeafSpy shows you the real-time 12V battery voltage, but that changes when you are driving as different accessories put different loads on the system (cabin fan, radio, heaters, etc.)
If you want LeafSpy to get a more stable reading, wait until you have not been driving the Leaf for a few hours. Then use LeafSpy to get a reading without actually starting the Leaf in drive mode.
You do this by first making sure every single accessory is off. No seat heaters, cabin fans, radio, lights, etc. Do this before you shut off your EV if you intend to measure the 12V battery later. Then while in your Leaf, start LeafSpy. It will complain that it can't get any data (because the Leaf is off obviously). Without putting your foot on the brake, start the Leaf into "standby" mode by pressing the power button twice in a row. The first press is just ACC mode for the radio/power ports, the second press will light up the dash and allow other accessory use (thought not recommended since that will just drain the 12V directly). In this test, it's ok to do this though as we only want to get a reading on the 12V battery. With everything off (mostly), you should hopefully see a battery voltage that is higher than 12.0 V, hopefully a lot more. If you see a voltage less than 12.0 V, it's possible the battery is just freezing (if you are doing this in freezing weather temperatures) or it may be the sign of a 12V battery in decline.