Android logcat readable buffer size is greater than total buffer size

Question

So recently I ran adb logcat -g on my Samsung Galaxy S10 Lite, and I got the following result:

main: ring buffer is 5 MiB (4 MiB consumed, 20 MiB readable), max entry is 5120 B, max payload is 4068 B
system: ring buffer is 2 MiB (1 MiB consumed, 10 MiB readable), max entry is 5120 B, max payload is 4068 B
crash: ring buffer is 512 KiB (128 KiB consumed, 43 KiB readable), max entry is 5120 B, max payload is 4068 B
kernel: ring buffer is 4 MiB (0 B consumed, 0 B readable), max entry is 5120 B, max payload is 4068 B

Now, I am very new to this, but why does readable buffer size is greater than the consumed one and total size?