sponge percentage issues

Stay with me folks, this makes my brain hurt..

When converting recipes from books into bakers percentages, what is the accepted method for dealing with the starter (or sponge)?

The way I've been doing it up to now is to include the flour and water from the starter/sponge in the recipe totals - so I end up with something along the lines of:

starter flour = 30%, dough flour = 70% TOTAL FLOUR = 100%, etc.

Another system is to treat the starter/sponge as a seperate ingredient within the dough and give it a total as a complete unit - i.e :

dough flour 100%. dough water 70%, sponge 25%, etc.

The sponge is then broken down separately, to determine it's own ratios independantly of the dough amounts.


Now, while the first method may seem the most straight forward, when I plug in the numbers from the original recipe they don't match! If I do it the second way they do.

What does everyone else use? Have I just been lazy by doing it he easy way?

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