TLS Fundamentals Ep.8 - Final Challenge

Hello together, 

i am stuck in the TLS Fundamentals final challenge at question 14. The question 

"Use the cipher suite DHE-RSA-AES128-SHA256 to connect on the port number found in the previous answer using TLS v1.2. What is the size of the Diffie-Hellman "Temp Key" used?"

If i am connecting to the local host with this command:

openssl s_client -connect localhost:8443 -cipher DHE-RSA-AES128-SHA256 -tls1_2

I get a connection fail, but if i use tls1_3, connection is working. But the found temp key value of 253 bits is not correct. Could you maybe guide me, where my mistake is?

Benjamin