How many "X"'s should I use to create temporary files safely and portably with `mktemp`?

From time to time, I create temporary files from shell scripts by invoking the command mktemp with 6 or more X's in the argument TEMPLATE. However, I am unsure if that amount will work with other implementations of mktemp because I have found commands with different amounts (e.g., [here](https://github.com/moby/moby/blob/1ffc120558bdfd528fc5740d6b6ea7c49f402639/Makefile#L252) , [here](https://github.com/Asana/kubernetes/blob/486ec2b7c9f95a43a856d1d71077382bf6b23afa/cluster/common.sh#L512) , and [here](https://github.com/torvalds/linux/blob/f5837722ffecbbedf1b1dbab072a063565f0dad1/tools/testing/selftests/net/big_tcp.sh#L7)) . I have researched a little bit and found the following: - The GNU implementation of mktemp requires three or more X's. - The OpenBSD implementation of mktemp appears to require six X's. However, I have little to no clue what the [underlying code](https://github.com/openbsd/src/blob/master/usr.bin/mktemp/mktemp.c#L80) does. - The manuals for the FreeBSD implementation of the [mktemp](https://man.freebsd.org/cgi/man.cgi?query=mktemp&sektion=1&n=1) command and [function](https://man.freebsd.org/cgi/man.cgi?query=mktemp&sektion=3&apropos=0&manpath=FreeBSD+14.0-RELEASE+and+Ports) are rather vague with how many X's the template should have.