According to the Financial Times Tether's market cap has fallen $7bn (9%) since 12th May to $76bn.
That is, $7bn has been redeemed into cash. These are redemptions where people are exchanging their Tether for real US dollars.
What does this mean?
So far Tether is managing to make the redemptions. Tether claim their coin is backed by US Treasury bills, which they are selling to meet redemptions. As long as they can continue to do this, the peg will hold and some of the fright will go out of the market.
The bad news is that redemptions of Tether into real fiat represents money leaving the exchanges. Those exchanges built around trading btc and alts against Tether, will see decreased trading volumes, and coins that are only traded on Tether exchanges, and don't have listings on fiat-based exchanges, are likely to see declines as no new money comes in.
Welcome to the crypto bear market.