Ann: Envirosuite Reports Q2 FY2021 Sales Update, page-82

They need to disclose if their holding changes due to the transaction by more than 1% of the total shares for the company they hold compared to their last disclosure. Smaller changes do not need to be announced, but obviously if there are several smaller changes accumulating than they need to disclose as soon as the total change is over the threshold.

EVS issued so far a total of 1,026,143,906 shares. 1% of that are 10,261,439 shares. If their holding drops (or rises) by more than this number since the last discloser they have to make an announcement. Selling or Buying of smaller amounts without disclosure is fine.