What does numbers mean in `mkfs -t ext4` command?

I have run:

mkfs -t ext4 /dev/nvme0n1

So I am getting output like that:

[2491.001727] EXT4-fs (dm-3): mounted filesystem with ordered data mode. Opts: (null)[2491.543355] EXT4-fs (dm-3): mounted filesystem with ordered data mode. Opts: (null)[2491.702837] EXT4-fs (dm-3): mounted filesystem with ordered data mode. Opts: (null)

What does 2491.702837 mean? HOw to determine the rest of process from such log?