In one study, when one identical twin had gender dysphoria, there was approximately a percent chance the other twin did too.

The correct answer is:

40%.

In the study Gender Identity Disorder in Twins: A Review of the Case Report Literature, out of 23 monozygotic female and male twins, nine (39.1%) were concordant for gender identity disorder (GID), best known as gender dysphoria. These conclusions allow considering a role for genetic factors in the development of GID.

would it be plagiarism to copy and paste off of here? ?

answer; beware of exaggerated claims without supporting evidence;