The FRT is the time it takes an agent to respond to a ticket for the first time. The typical FCT time is 15 minutes. It is critical to keep it as low as possible because customers become frustrated when the first response from support takes too long.
The FCT of an agent should be within the response time (configured in the SLA policy). If an agent has a high average FCT but her tickets frequently violate SLAs, it indicates that she has more tickets than she can handle.