This is the graph that you first see when you get into Transaction Detail View. To get to this view, you can simply click on the arrow to the very right of a transaction when in the dashboard. The Transaction Detail view gives you more data that is specific to the transaction you've selected, whereas the Dashboard gives you a quick way to see how your flood ran as a whole.
First of all, the green bars in the test represent the number of passed instances of this transaction. Flood reports HTTP 200s as passed and all HTTP 4xx and HTTP 5xx as failed by default. Adding validations or assertions can change this behaviour.
There are a few icons that you may see in the Transaction Detail View that come in different shapes and sizes. These icons correspond to status codes.
green diamonds - HTTP 200
purple crosses - HTTP 4xx
red square - HTTP 5xx
blue circle - non-HTTP response
If you ever need help deciphering your test results, we're always happy to have a chat with you!