The number of /dev/pts entries available is dynamic up to a limit determined by the amount of physical memory available on the system. pt_cnt is one of three variables that determines the minimum number of logins that the system can accommodate. The default maximum number of /dev/pts devices the system can support is determined at boot time by computing the number of pty structures that can fit in a percentage of system memory (see pt_pctofmem next). If pt_cnt is zero, the system allocates up to that maximum. If pt_cnt is non-zero, the system allocates to the greater of pt_cnt and the default maximum.
0 to maxpid
When you want to explicitly control the number of users that can remotely log in to the system.
For information, see pt_cnt (Pre-Solaris 7 and the Solaris 7 Release).