In this paper of Maja Volkov, the authur metions a number called "défaut de semi-stabilité" on page 9. It is defined as $\text{dst}(E)=\frac{12}{\text{pgcd} (12,v_p(\Delta_E))}$ where $E$ is an elliptic curve over $\mathbb{Q}_p$ and "pgcd" is the greatest common divisor.

Then the authur says on the next paragraph that if $p>5$ and $E$ has potential good reduction over $\mathbb{Q}_p$, then $e=\text{dst}(E)$ is prime to $p$ and $E$ has good reduction on an totally ramified extension of $\mathbb{Q}_p$ of degree $e$.

So the question is how to prove the two propositions and I want to know if there are some reference about the relations between "défaut de semi-stabilité" and the reduction types of elliptic curves.

Thanks!