Difference in node memory stats from "oc adm top node" and "free" commands

Issue

After installation of metrics-server in OCP 3.11, there is a significant discrepancy in the output between the commands oc adm top node and free -h.

# oc adm top node

NAME            CPU(cores)   CPU%      MEMORY(bytes)   MEMORY%
abc-node        1030m        1%        228483Mi        88%  

Here the consumed memory seen is around 88% of the total memory.

# free -h

       total   used        free      shared    buff/cache     available
Mem:    251G    21G         14G         18M        215G         227G
Swap:            0B          0B          0B

Whereas, the free command shows that the consumed memory on the same node is 21G, which is very distant from oc adm top node command.