australia – Australian Visa date – confused arrival date

I got a Visa of 18 months for Australia I have but, visa dates are confusing me as it says:

Granting date is 07 February 2020 ;

First arrival by 07 August 2020 ;

Must not arrive after 07 August 2020.

And in the note, it is shown as the visa of 18 months starts calculated from the date of the first arrival.

My questions are,

  1. From beginning what date my visa starts for 18 months?
  2. As in the note of the visa, it is said that the visa of 18 months would start after the first arrival in the country, but would it be calculated for 18 months after my arrival date 07 August 2020?