Hi,
I am seeing this issue in openssl-1.1.1d.
These are the steps to see the negative value.

• Start with a default SSL_CTX, initiate a TLS 1.3 connection with SNI, "Accept" count of default context gets incremented
• After servername lookup, "Accept" count of default context gets decremented and that of SNI context is incremented
• Server sends a "Hello Retry Request"
• Client sends the second "Client Hello", now again "Accept" count of default context is decremented. Hence giving a negative value.

Please let me know if you need any more information on this.