Add items in the page > first page, the state shows wrong totalPages

[nttdocomo]

var pageCol = new PageableCollection([],{
        mode:'client',
        state: {
            pageSize:5
        }
    }),
    array = []
    for (var i = 7 - 1; i >= 0; i--) {
        array.push({
            'name':i,
            'phone':'15210492508',
            'amount':i,
            'comment':'cccccccccccccc'
        })
    }
    pageCol.add(array)
    pageCol.getNextPage()
    pageCol.add(array)
    console.log(pageCol.state)

At last, the log will show the state's totalPages is 3, but expect is 2.