After allocating the enough resource in the memory parameter in PostgreSQL why SWAP memory is fully utilized.?

Question

I have one production server in which below are the resource provisioned.

RAM: -256 GB
CPU: -64

i have set the below configuration after the resource allocated in the postgresql.auto.conf file: -

shared_buffers = '74GB'
effective_cache_size = '150GB'
maintenance_work_mem = '10GB'
work_mem = '4GB'
max_worker_processes = '64'

max_locks_per_transaction = '512'

After allocating tha much resource still SWAP memory has fully used:-

[root@xx-xx-xx-xx data]# free -g
              total        used        free      shared  buff/cache   available
Mem:            251           6           4          73         240         171
Swap:             7           7           0

Can anyone help me with this issue. Is i have set something wrong in the tunning parameter. Also, how we can check the query is taking all the RAM which i have set.