I am not sure what you are asking...
Generally speaking Number fields will either have 0 instead of an empty string or if it really is 'blank" then it is NULL which does act differently than 0 (the same can be said of a blank string or a NULL string field).
If you are looking how to make a 0 look like ' ' then conditionally suppress the field as
{table.numberfield}=0
and it will make it look like an empty string.
Is that what you are asking?