Why is this an issue?

When using a case statement to alternate between different values of an enumeration, all values should be handled. This could be done explicitly by including all values in the case arms, or implicitly by adding a default branch.

An exhaustive case statement makes it clear that all behaviour is intentionally defined for all values, and guards against accidental omissions - for example, forgetting to update the case statement when a new value is added to the enumeration.

Note that this rule currently ignores any case statement with a subrange expression due to analysis constraints.

How to fix it

Add the missing enumeration values to the case:

type
  TBeverageKind = (bvCold, bvFrozen, bvHot, bvRoomTemp);

procedure PrepareBeverage(Kind: TBeverageKind);
begin
  case Kind of
    bvCold, bvFrozen:
      Refrigerate;
    bvHot:
      Microwave;
  end;
end;

type
  TBeverageKind = (bvCold, bvFrozen, bvHot, bvRoomTemp);

procedure PrepareBeverage(Kind: TBeverageKind);
begin
  case Kind of
    bvCold, bvFrozen:
      Refrigerate;
    bvHot:
      Microwave;
    bvRoomTemp:
      // No action required
  end;
end;

Alternatively, add an else block to implicitly handle all remaining values:

type
  TBeverageKind = (bvCold, bvFrozen, bvHot, bvRoomTemp);

procedure PrepareBeverage(Kind: TBeverageKind);
begin
  case Kind of
    bvCold, bvFrozen:
      Refrigerate;
    bvHot:
      Microwave;
  end;
end;

type
  TBeverageKind = (bvCold, bvFrozen, bvHot, bvRoomTemp);

procedure PrepareBeverage(Kind: TBeverageKind);
begin
  case Kind of
    bvCold, bvFrozen:
      Refrigerate;
    bvHot:
      Microwave;
  else
    // No action required
  end;
end;