You are right, the zone limit is 63 (64 technically, with the 0=firewall zone). My recommendation is you upgrade the CC to 5.3.2P04. CC 5.3.1 is no longer supported; perhaps you're running in to some issue that is already fixed. 5.3.2P04 has a fix for the Bash Shellshock vulnerability also; this will not be fixed in 5.3.1 as it's not a supported version.
If, after you upgrade to 5.3.2P04, you are still getting this error, I suggest filing a Support ticket and doing a remote session so we can see what's going wrong.