What does imageFs usage metric mean in kubernetes/openshift

Question

i am trying to understand the pod ephemeral storage usage on openshift cluster, i am using method suggested here How can I determine the current ephemeral-storage usage of a running Kubernetes pod?

i dont understand what imageFs metric means and how its calculated, on one of the node the imageFS metric looks like this

[ocuser@client-1 ~]$ curl -k -s -H "Authorization: Bearer $(oc whoami -t)" $(oc whoami --show-server)/api/v1/nodes/${node}/proxy/stats/summary | jq -r '.node.runtime.imageFs'
{
  "inodesUsed": 4702515,
  "inodes": 268172736,
  "inodesFree": 263470221,
  "usedBytes": 449863632679,
  "capacityBytes": 549207388160,
  "availableBytes": 281833754624,
  "time": "2023-09-27T09:11:49Z"
}

the above metric says 419G of imageFs is being used, while the node Disk capacity is 512G and still says 263G is available should'nt the available space be 512-419=93G ??

for sake of clarity here are my node FS usage metrics, which looks fine as usage and availability metrics checks out

[ocuser@client-1 ~]$ curl -k -s -H "Authorization: Bearer $(oc whoami -t)" $(oc whoami --show-server)/api/v1/nodes/${node}/proxy/stats/summary | jq -r '.node.fs'
{
  "inodesUsed": 4702439,
  "inodes": 268172736,
  "inodesFree": 263470297,
  "usedBytes": 267227099136,
  "capacityBytes": 549207388160,
  "availableBytes": 281980289024,
  "time": "2023-09-27T09:10:58Z"
}

sh-4.4# df -Th /
Filesystem     Type  Size  Used Avail Use% Mounted on
/dev/sda4      xfs   512G  249G  263G  49% /

*adding edits just to keep the question active