Why different CPU count from nproc and nproc --all in OpenVZ container?

I'm trying nproc and nproc --all in an OpenVZ container to count the number of CPU threads assigned to the vps by upstream provider. While nproc resulting 1, nproc --all resulting 24 CPU threads. May anyone please help me in explaining this? The upstream provider is supposed to assign only one CPU and cat /proc/cpuinfo is also saying that. Then from where and how this 24 is coming? Please find a screenshot here . I'm using CentOS 7 inside the vps.