Your first move must be a complete meld
In a game where this rule is in place, the first cards that you play in a game must form one or more entire melds with only cards that come from your hand. It is not allowed to add your cards to existing melds on the table, or to combine your first cards with other cards from the table.
Melds must be a minimum number of points
If this option is set, the meld or melds that you form in your first move must be of at least a given minimum total number of points. If you cannot reach that total number of points, then you cannot play yet.
For example, a meld of J*KA counts as 37 (11+12+13+1).
Other moves are allowed in the same first turn
If this option is set, then after you have played these complete melds (with the minimum number of points, if applicable), you may play other moves. Like adding cards from your hand to melds on the table, or make combinations.
Games with this rule
In Rummi, Tile Rummy, Easy Rummi, Wooden Rummi and World Champs Rummi have the rule that you must play a meld of 30 as your first move. In Rozzy you must play a complete meld but there is no minimum; other built-in games in Rummi don't have this rule.
In some Rummy type games, a variation of this rule applies. In Rummikub®, you usually have to play complete melds of minimum 30 as your first move.