Unspayed females can show swelling well ahead of bleeding. Sometimes they do not bleed much at all and some females are so clean you don't see the bleeding. the first heat there is typically a LOT of swelling. The best thing is to check for bleeding using a white tissue.
Heats are usually 21 days (can be more or less, but that is typical). The dog starts with swelling and bleeding. The blood becomes less pronounced and stops.. and this is when she enters standing heat and will be receptive to males. After this period she will typically bleed again and then be finished. If NOT breeding your bitch, from the time of swelling to the final bleed off she should be sequestered from male dogs.