Hello.I would like to know whether I need 2x culture media when...

If the cell is in pellet form, you need 1X media. If the cell already is in some volume media, such as 10 mL 10% RPMI, you only need 1X media, too. Doing so only dilutes cell concentration. Unless you need to add two kinds of media at same time to the cell pellet, under that situation, you need 2X(20%) RPMI, and 0X(0%) RPMI to become 10% RPMI. Remember the "X" means serum concentration.