How to Limit CPU Cores in Virtualmin?

SYSTEM INFORMATION
OS type and version Ubuntu Linux 20.04.4
Virtualmin version 6.17-3

I am sole owner of my server and all the virtual servers. I want to limit the resources being used by servers. Currently I set up ram usage by editing limits.conf file like this -

oneofmyuser hard memlock 1024

Now im confused with the cpu option there in example codes -

#Where:
#<domain> can be:
#        - a user name
#        - a group name, with @group syntax
#        - the wildcard *, for default entry
#        - the wildcard %, can be also used with %group syntax,
#                 for maxlogin limit
#        - NOTE: group and wildcard limits are not applied to root.
#          To apply a limit to the root user, <domain> must be
#          the literal username root.
#
#<type> can have the two values:
#        - "soft" for enforcing the soft limits
#        - "hard" for enforcing hard limits
#
#<item> can be one of the following:
#        - core - limits the core file size (KB)
#        - data - max data size (KB)
#        - fsize - maximum filesize (KB)
#        - memlock - max locked-in-memory address space (KB)
#        - nofile - max number of open file descriptors
#        - rss - max resident set size (KB)
#        - stack - max stack size (KB)
#        - cpu - max CPU time (MIN)
#        - nproc - max number of processes
#        - as - address space limit (KB)
#        - maxlogins - max number of logins for this user
#        - maxsyslogins - max number of logins on the system
#        - priority - the priority to run user process with
#        - locks - max number of file locks the user can hold
#        - sigpending - max number of pending signals
#        - msgqueue - max memory used by POSIX message queues (bytes)
#        - nice - max nice priority allowed to raise to values: [-20, 19]
#        - rtprio - max realtime priority
#        - chroot - change root to directory (Debian-specific)

How can I limit my user to use only 1 or 2 cores?
There is core value but it should be in Kb? I want to limit to for example 2 cores? So how many kb?
Also for cpu ?
What are the ideal values for these options for a normal server with normal wordpress site ?

Hi,
Is it only possible with Ubunto or can I limit my CPU Cores in Windows too?

Only for Ubuntu limits.conf.
for Windows, looks for other tutorials.