Mandarin Neutral Tone: Tone Value?
The neutral tone doesn't have a fixed value; it's phonetic realization is largely determined by the preceding tone:

Also called fifth tone or zeroth tone (in Chinese 轻声 [輕聲] qīng shēng, literal meaning: &quot;light tone&quot;), neutral tone is sometimes thought of as a lack of tone. It is associated with weak syllables, and thus usually comes at the end of a word or phrase, and is pronounced in a light and short manner. The pitch of the neutral tone depends almost entirely on the tone of the preceding syllable. [...]
First ˥   ˨ 2 玻璃  bōli    glass   ˥.˨
Second ˧˥ ˧ 3 伯伯  bóbo    uncle   ˧˥.˧
Third ˨˩  ˦ 4 喇叭  lǎba    horn    ˨˩.˦
Fourth ˥˩ ˩ 1 兔子  tùzi    rabbit  ˥˩.˩