Dynamic Markings

[Len]

I've been creating notation software files from ragtime sheet music and have come accross sections of music which have two dynamic markings seperated by a dash. e.g. pp-f, p-f, or p-mf. The second mark is always louder than the first.

Does anyboy know what this means.

Common sense tells me that it could mean begin with the first marking and graually increase to the second mark, but I also think that it may be shorthand for play through with the first marking and then use the second marking when repeated.

Any comments would be appreciated

Thank you