A particle has a primary sense, but context can permit a recognized secondary use. Fa is sometimes used with the conjunctive force of waw.
«له علي درهم فدرهم»
I owe him a dirham followed by another dirham.
The textbook explains this debt acknowledgement as imposing two dirhams. The expression combines two amounts; the use of fa does not reduce the obligation to the first dirham only.
Keep primary and figurative senses distinct: connected succession is fa’s usual sense, whereas this acknowledgement foregrounds conjunction.