And to explain this further the values are:
Horizontal offset, vertical offset, blur radius, spread radius, shadow colour.
Although these are visually separated with commas here for ease of reading the values should be separated only by a space, not a comma. The only times you'd use commas are within rgb or rgba colour specifications and if you're stacking up multiple shadows in one box-shadow extended property. This is a really cool capability if you'd like to try for something a little more photorealistic, or at least a little less corny. Each complete SET of values must be separated by a comma. The example below strings two shadow values together to create a large hazy pale shadow (using rgba to set half-strength/0.5 opacity) and a denser one (although grey rather than default black shadow colour) more immediately 'behind' the object:
0px 10px 10px -5px rgba(0,0,0,0.5), 0px 25px 30px gray
Put that straight into the 'value' part of an object's Extended Properties 'box-shadow' name and preview in a browser to see how it looks. Have fun!