I am trying to put the description "HUC # is 10190020302" under the Label "PSICC HUC 12" but I could not find a way in ArcGIS Pro 3.3 . Has anyone in here tried this before or have done this before?

Because I asked , the Legend I want need to be "tighten" and I have a map that is almost cover all over the page on 5.8 x 11 letter.
Thanks !
Thanks !