A CSCS account number can be different from another CSCS account number, but a CHN is supposed to identify the investor. CSCS describes CHN as a unique number identifying an investor in the Nigerian capital market.

I think the mix up is coming from when you were choosing the stockbroker.
If I am getting your question right…

Your friend already had:
Afrinvestor 2.0 account
CSCS Account No. A
CHN A
Then, while subscribing for the Dangote Refinery IPO through the NGX electronic application process, the system appears to have created/assigned:
IPO application
CSCS Account No. B
CHN B right? If it is that so..
That does not automatically mean the IPO money or shares are lost.

I think what is best now is that your friend
Contact Afrinvestor immediately
Email or contact Afrinvestor telling them that:
“I already had a CSCS account and CHN with Afrinvestor. I subsequently subscribed for the Dangote Refinery IPO through the NGX electronic application channel and the application generated a different CSCS account number and CHN. Please confirm which CHN was used for my IPO subscription and ensure that my existing investor identity is properly linked/consolidated.”

Ask them specifically to check the IPO application using the friend’s:
Full name
Existing CHN
Existing CSCS account number
New CSCS account number
New CHN
IPO app

Ask Afrinvestor one very specific question
“Which CHN will receive the Dangote Refinery IPO shares if my application is successful?”
That’s the question I would want answered.
Because the important thing isn’t merely that two numbers exist. We want to establish where the IPO allotment will be credited. Do you get?