Van Khanh, the international IPA transcription is confusing, because with some affricate consonants it uses two characters to represent one sound, as Mister Micawber mentioned. It does that with [tS] (the “ch” sound in English) and with [dZ] (the “j” sound in English).
These affricates consist of two sounds: a stop followed by a fricative. However, in English they function together as one unit. For this reason, when we teach phonetic transcription to teachers in America we often don’t use the international version of IPA, but the American variant instead. In the American version the [tS] consonant is written as a C with a hacek over it, and the [dZ] consonant is written as a J with a hacek over it. This eliminates the confusion that arises when two letters are used to transcribe one consonant.
A hacek is a circumflex (^) written upside down. I tried to write the actual phonetic characters, but this site is not Unicode compliant, so it wouldn’t show them after I put them in.