(P) means that this project is on pause (mouse over hint shows this as well). A project enters this stage if you use the option to pause if a certain amount of verified or submitted urls have been reached.
A pause is also happening when the tier project has no urls to build links for. That can happen if you have no verified urls in the main project or the tier filter would remove them again so that no links are there.
Comments
but if all projects are made into tier 1 tier 2 tier 3 there will be a P sign
like this