The ability of a MikroTik Cloud Core Router (CCR) 1009 router to support a specific number of users depends largely on the type of traffic, the network configurations applied, and the specific tasks being performed through the router.

There is no exact number of “supported users” because it varies depending on use. However, the CCR1009 is a high-performance device designed for enterprise and Internet Service Provider (ISP) applications, meaning it is built to handle a significant amount of traffic and process data efficiently.

If you currently have around 350 users and are only using around 10% of the CCR1009's processing power, that suggests the device is handling the workload quite comfortably.

This also indicates that, in theory, you could support many more users, as long as the usage pattern and traffic type remain relatively constant and you do not introduce additional services that require more processing power.

It is important to consider several factors when evaluating a router's ability to support users:

1. Traffic Type: Data-intensive applications such as video streaming, online conferencing, and online gaming consume more resources than web-based activities or email.
2. Active Services: Features such as firewall, NAT, VPN, content filtering, and QoS can increase the load on the router's processor.
3. Total Bandwidth: The link capacity of the Internet and the distribution of bandwidth among users are also crucial. Make sure your Internet link and bandwidth settings on the router can handle the demand.
4. Security politics: Complex firewall rules and additional security configurations may require more processing.

Although your CCR1009 appears to be working well with 350 users, it is advisable to continue monitoring system performance as the number of users increases or the usage pattern changes. MikroTik RouterOS provides several tools for monitoring performance, such as graphs, CPU profiles, and traffic logs, which can help you identify bottlenecks and optimize configurations.

In summary, although there is no official maximum number of users for the CCR1009, your experience suggests that the device is capable of handling more users than you currently support. However, maintain ongoing monitoring to ensure performance is maintained as your network grows or changes.