I've asked support, and they've re-installed PHP with bcmath, and they also ask this,
"I have reinstalled the BC Math for php in the server, still the webpage seems to report same error. Can you please check with the Chevereto support and ask why those messages come even if the BC Math function is enabled."
Chevereto uses the php function "function_exitst" to tell if that functions are enabled or not. Is not Chevereto saying that those functions are not available, is PHP.