You want to know the maximum value that can be set as SSL session cache size via hidden CLI command "#(config ssl)set-session-cache_size". This command is applicable for proxySG, ASG and SWG VA products.
Hidden command "set-session-cache_size" has been added from SGOS 22.214.171.124. Regardless of the HW model / platform SSL session cache acceptable value can be between 1 and 100,000 from starting SGOS 126.96.36.199 up to below SGOS / ASG versions
Starting with below SGOS / ASG versions SSL session cache Acceptable value can be between 1 and 1,000,000
Increasing SSL session cache size on your appliance will utilize more memory(RAM). If necessary consult with Symantec support before increasing SSL session cache size. To determine the default session cache size please follow this article TECH247146