How to edit secondary lightbox

Hi! Does anyone know if there is a way to edit the text in the secondary lightbox (the one that pops up when I click an image)? Right now the text takes up about a third of the secondary lightbox and the rest of the box is filled in black. A screenshot is here: http://ampedforeducation.org/wp-content/uploads/2014/10/Screen-shot-2014-10-31-at-10.43.40-AM.png

Thanks!

https://wordpress.org/plugins/lightbox-plus/