Having the same field name is a problem, at least for those using JavaScript. If you say entry().set("fieldName", 0), memento has to know which fieldName you want set. It'll pick one, but it may not be the one you intended.
I haven't done much of this in Memento, but in general, the first row of the CSV file contains the column names, generally all distinct from each other. The remaining rows contain the values that go into those columns. Text fields should have quoted values in the CSV file, while numeric fields' (like Integer, Real, & Currency) values do not need quotes.