Additional Dextrose is required when kegging to ensure the alcohol level of the finished beer is correct.
The secondary fermentation during the bottling stage is not available when kegging and force carbonating via a CO2 cylinder.
This convenient 1.2kg Dextrose pack compensates for secondary fermentation during primary fermentation. It replaces the normal 1kg of sugars / malts used with kit tins.
If you are kegging and using malts / other fermentables instead of the normal 1kg of Dextrose, then add 200g of Dextrose Kegging Supplement (Product code 84505).