In this regard, for 17-18 when the ITC was availed in 18-19, CBIC had issued a Press release which may be useful to you.
"Many taxpayers have represented that Table 8 has no row to fill in credit of IGST paid at the time of import of goods but availed in the return of April 2018 to March 2019. Due to this, there are apprehensions that credit which was availed between April 2018 to March 2019 but not reported in the annual return may lapse. For this particular entry, taxpayers are advised to fill in their entire credit availed on import of goods from July 2017 to March 2019 in Table 6(E) of FORM GSTR-9 itself."