When Mif2Go encounters in your FrameMaker document an equation, which is a MathFullForm object, Mif2Go generates a DITA <image> element for the equation. You can also have the original MathFullForm included as the content of the <alt> tag.
To include MathFullForm equations in <alt> tags:
; MathFullForm = No (default) or Yes: include MathFullForm objects
; in DITA <alt> tags for equations.
See Figure 5.9.1 Understanding how equations are processed.