question

You can use a Decision Point activity that 75% of the time starts the activity that makes companions while the other 25% of the time it starts either a different activity or the activity after the companion creation activity. Basically you want to use the decision point activity to branch your logic.

In the Next Activity field of the Decision Point activity you'll find a Based on Percentages pickoption that you'll find useful.

Alternatively you could put some code right into the trigger where the companions are created.

In HC there's a simplified command, P(), for doing things by percentage. For example, the code in this if statement would fire 75% of the time:

if( P(75, 1, 25, 0) )
{
	//Do Something
}

So you could open up the code editor for the trigger that's creating companions and wrap the trigger in an if statement like the one above.