What happens when you do not use enough yeast?

[Matt76]

i'm running a UJSM and it's been fermenting for 6days now. I'm just wondering if I didn't use enough yeast. I was told 1packet would do a 5gallon ferment however, after looking closer I believe I should have used 2packets. Does it just take longer to ferment??

This is however, the first run so I believe after distilling I will be able to correct the problem on the second ferment by adding another packet in the mix