When you enter a ring game, you take a certain number of chips with you to the table to play. These chips are called chips in-play. Your chips in-play are not included in your chip total, so when you enter a ring game they will be deducted from your total chip amount. While you're at the table, it might appear as if you're missing those chips. When you leave the table, the chips that you've earned plus the original chips or the chips you have remaining are returned to your total. If you busted out, no chips are returned.
The reasoning for this is that chips cannot be in two places at once. If the chips that you brought to the table were still showing in your total balance while you played, it would be easy to confuse your total chip amount. This situation might end up with a player trying to buy into another game that they don't actually have enough chips to buy into.
When you leave a ring game table, the chips that you've earned at the table in addition to the remaining chips in-play that you have will be returned to your chip total after the end of the next pot. Sometimes it can take a few moments for your chip total to update once you leave a table, but usually a quick refresh of the page solves it! If your chips still haven't returned to your total after waiting a few minutes and a refresh of the page, please check out our I won chips. Where are they? article.