For the record...

Inside, Website > your site > Content > PHP 7.0 FastCGI > PHP > PHP.ini value

max_execution_time = 600
request_terminate_timeout = 600

Inside, Website > your site > Advanced

location ~ \.php$ {

[...]        

include fcgi.conf;        
fastcgi_pass unix:/var/run/ajenti-v-php7.0-fcgi-over-php7.0-fcgi-0.sock;
fastcgi_read_timeout 600;

[...]
                  }

If it can help?