UILabel 设置字体大小不一

NSString *str = [NSStringstringWithFormat:@"￥%@",model.total];

    NSMutableAttributedString *mutStr = [[NSMutableAttributedStringalloc]initWithString:str];

    NSRange range =NSMakeRange(0,1);

    [mutStr addAttribute:NSFontAttributeNamevalue:[UIFontsystemFontOfSize:13]range:range];

    _offSetLabel.attributedText = mutStr;