558.Section 228 applies the extended sentence to those aged under 18 whom the court considers to pose a significant risk of serious harm as defined in subsection (1)(b). Where the offender has been convicted of a specified offence the court must impose an extended sentence, unless the offence is a serious offence and the case is one in which a sentence under section 226 is appropriate. The sentence operates in the same way as it does for adults, but is a sentence of detention rather than imprisonment.