How much should we bend during ruku? Is it enough if we bend until all the finger tips (including the thumb) reach to the knees?

If we misunderstood earlier his emminence fatwa and we performed ruku while only bending to the extent that only the 4 finger tips (exluding the thumb) reaching to the knee – do we need to repeat those prayers?

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It is enough to bend until the four fingers reach the knees