The issue here is that the number is a scripture reference. Paratext automatically checks references that are in \r and \xt fields, but does not check references if they are not marked.
In the introduction, references can be marked with (\xt 1:1-13\xt*) or if it is part of the introduction outline (\ior 1:1-13\ior*)
If you are using \ior, the () can be placed inside of the markers: \ior (1:1-13)\ior* since the outline reference assumes the book name. With the \xt markers, Paratext will report an error with the book/chapter seperator if the ( is inside of the \xt.