In the illustrations of the IPA Handbook, this letter may come before a word or syllable to indicate prosodic pitch, and after a word or syllable to indicate lexical tone.
When this symbol occurs in combination with other tone letters, they indicate the pitch contour of the tone. For example, ˧ means a level mid tone, and ˨˩˦ means one that begins low, then goes extra-low and ends high.
Tone letter on Wikipedia.Wikipedia 