Why does my materials beginning inventory for all time show an amount?
If your material beginning inventory shows an all time amount, it is usually due a starting inventory adjustment that is linked to one of your materials. This most likely was set when you first created your Materials. As starting adjustments don't have a date associated to them (i.e. they are the stock you had on hand when "records began") they are always assumed to be the starting amount and value no matter how far back in the date range you go.
If you want to have these adjustments appear only within a specific date range, what you'll need to do is find and set these starting adjustments to zero and then create a material expense instead, to account for the increase in stock with the correct date range.
To locate the starting adjustments you need to change, if you haven't yet added any manufactures or other manual adjustments, you may be able to look at your materials list page for materials where the value in the Purchased column is not the same as the In Stock one. This indicates that you have an inventory adjustment for this material.