TT Segment Shares are a particular category of stocks where Settlement of securities will be done without any netting off of positions. If you have sold shares so notified, you will have to mandatorily give delivery. Any purchases have to be separately paid for and delivery taken. Therefore, even after any subsequent purchase in the same settlement, the blocks on your DP balances will remain till settlement.

Basically, its a TT Segment is a category of shares where you cannot day trade on them. You need to take delivery of shares and hold for 2 days before selling them.