By default, Mif2Go splits each FrameMaker file into individual DITA XML topic files, one file per topic. To have Mif2Go generate instead a single multi-topic DITA XML file from each FrameMaker file (not recommended):
When SplitTopicFiles=Yes, Mif2Go splits each chapter file on topic boundaries identified by FrameMaker paragraph formats; see §14.9.1 . A topic ends at the start of the next topic, or at the end of the FrameMaker file. When you split a FrameMaker file into individual DITA topic files, the hierarchical relationship among those topics is made explicit in the map levels assigned to those topics; see §15.2.2 .
When SplitTopicFiles=No, unless you nest the topics from each FrameMaker file so there is just one top-level topic, Mif2Go wraps all topics within a top-level <dita> element. See §14.8.4 .