Adjusting chocolate amount based on the percentage: Kitchen Confectionery

I am reading the book, 'Cooking with Chocolate'.  One of the discussions concerns adjusting the quantity of chocolate  based on the percent of the chocolate being used if it differs from that called for in the recipe.  Example - recipe calls for 330 g of 70% chocolate OR 350 g of 60% chocolate, etc.
There is no formula included to make the conversion dependent on the amount of chocolate called for in my recipe - a recipe of my own not contained in the book.
Does anyone have any reference that I can access?
I would imagine that an increased amount of chocolate with a lessor percentage would also affect the volume of the entire recipe.  Thanks, Barb

PS - I apologize if this is a duplicate but did not see any indication of the message being sent.B