The ICA number is not directly related to the Visa Developer Portal, therefore, I will not be able to comment directly on how you will get the ICA number.
To provide you with further assistance, can you please let me know the following:
The Visanet number is not assigned by Visa. The "iat" (issued at) claim identifies the time at which the JWT was issued. This claim can be used to determine the age of the JWT. Its value MUST be a number containing a NumericDate value. Use of this claim is OPTIONAL. telldunkin
Visanet number is for the occasional web token and it is for standard industry technology. It is for building a case in the web token. The IAT number, is a number that is assigned by a developer who is generating the token. The IAT number is generated by the developer creating the web token and is industry standard.