Railsで複数の項目でgroupしたデータの加工

Question

Railsで複数項目でGroupして帰ってきた結果の配列があります。

{"[1, 16, 13, \"2022-01-11\", 3, 1]":1,"[1, 16, 13, \"2022-01-11\", 3, 2]":1,"[1, 16, 13, \"2022-01-11\", 3, 3]":1,"[1, 16, 13, \"2022-01-11\", 3, 4]":2,"[1, 16, 13, \"2022-01-11\", 3, 5]":2,"[1, 16, 13, \"2022-01-11\", 3, 6]":1,"[1, 16, 13, \"2022-01-11\", 3, 7]":1,"[1, 16, 13, \"2022-01-12\", 3, 1]":1,"[1, 16, 13, \"2022-01-12\", 3, 2]":1,"[1, 16, 13, \"2022-01-12\", 3, 3]":1,"[1, 16, 13, \"2022-01-12\", 3, 4]":2,"[1, 16, 13, \"2022-01-12\", 3, 5]":2,"[1, 16, 13, \"2022-01-12\", 3, 6]":1,"[1, 16, 13, \"2022-01-12\", 3, 7]":1}

このデータを下記のように加工したいです。

[
["2022-01-11",{"1":1,"2":1,"3":1,"4":2,"5":2,"6":1,"7":1}],
["2022-01-12",{"1":1,"2":1,"3":1,"4":2,"5":2,"6":1,"7":1}]
]

下記の部分のKeyは

{"1":1,"2":1,"3":1,"4":2,"5":2,"6":1,"7":1}

最初のデータのKeyになっている配列の最後の要素です(indexの6)。

[1, 16, 13, \"2022-01-11\", 3, 1⇦この部分]

以上わかる方いらっしゃいましたらよろしくお願いいたします。