0 to go! Will appear when you have maxed a gag track. After you have maxed this gag track, where it once said how much experience points you needed for your next gag, there will now be a 500 to go bar.
If you have not used your new level 7 gag by the time you get the 500 experience points, you will encounter this 0 to go bar.
Your experience bar will stay at 0 to go until you use your level 7 gag. Once you have used your level 7 gag, you will earn it back immediately after the cog battle you used your level 7 gag in. After you get your level 7 gag back, the experience bar will go back to 500 to go!