Added Dragons to your wallet does not reset your score. The simple formula would be:
1st batch of Dragon Days of Slumber Score (Time x Quantity) + your 2nd batch + your 3rd batch + ... = Total Dragon Slumber score
Moving Dragons will affect your score in Last In First Out accounting style. Meaning if we take the example above, the quantity of the 3rd batch would be adjusted before your 2nd and 1st batch.