After how many days of ovulation embryo implantation occurs?

Ans-B i.e. 7-9 days Shaws states "Implantations occurs about 6th day after fertilization or approximately 20th day of a regular menstrual cycle " Guyton states (10th/e, p 945)"After reaching the uterus, the developing blastocyst usually remains in the uterine cavity for an additional 1-3 days before it implants in the endometrium, thus implantation ordinarily occurs on about 5th to 7th day after ovulation" 10th/ep. 945.But on page (936-937) of the same edition, Guyton clearly state "From the time a fertilized ovum enters the uterine cavity from the fallopian tube (which occurs 3-4 days after ovulation) until the time ovum implants (7-9 days after ovulation) the uterine secretions called uterine milk provides nutrition for the early dividing ovum."