What is a Signature and how to switch it off?

Signature "Do you want a similar calculator on your web? Sign up Free to Calculoid.com" can be seen below every embedded calculator. Users with subscription are able to switch it off in calculator configurations. If you have a free plan, you have to purchase any paid subscription to be able to switch the signature off. 

To switch the Signature off, go to your Calculator > Configure > Signature > Hide.