All calculations done by the spreadsheet start with the following fundamental assumptions:
A pound is equivalent to 453.592 grams. Some cookbooks use the roundedvalue 454, and the results should be extremely close. Differences, however may show up in the fractional part of computed results.
A cup of water is equivalent to 236.588 grams, or rounded to 237 grams. This is only true (strictly speaking) for pure water at a temperature of 39.2 F (4 C). At temperatures below, and above, water is less dense and would occupy slightly more volume. This temperature effect may be ignored in practice. Liquids (or solids) other than water, have a specific gravity different from 1, and this needs to be taken into account when converting.
When converting weights to volumes, aside from the issue of how the calculation is done, there is the question of representation. To scientific, and obvious, way is to display a result in decimal notation. While this is correct, most bakers that use volume measurements do not have measuring cups and spoons that are marked with a decimal scale. Rather that use cups and fractions like 1/4, 1/3 and 1/2, or they use tablespoons or teaspoons (and fractions). Thus the spreadsheet attempts to display results in such units, approximating to the nearest fraction typically available in measuring cups or spoons.
All calculations in the spreadsheet are done in very high precision, and intermediate rounding is avoided. Thus the only rounding takes place when results are formatted for display. This can lead to some surprises. It is not unusual, for example, to see a flour weight in a recipe of 328 g, and yet when the value "328" is entered in the "Reverse Worksheet", the calculated percentage is not identical to the one in the recipe. This happens because that value in the recipe was rounded to whole grams, which means the true value may have been different by as much as half a gram.
Whenever you wish to use the result of a calculation elsewhere, it is therefore best to link to the cell containing the value, or to do a copy, followed by "Paste Special>Values". Some of the result columns (in the "Recipe Worksheet" for example), do not use a cell format, but rather compute the displayed units in VB code. Therefore these cells contain text, rather than numerical values, and referring to them, or copying them will not work as desired. Always base your calculation no the decimal pounds column.