Can you provide my with more details of reading this chart and how did we get these results from it

Figure 8.1 Cumulative Abnormal Returns Before Takeover Attempt:s FIGURE 8.1 Cumulative abnormal returns before take- over attempts: Target companie Source: Arthur Keown and John Pinkerton, "Merger Announcements and Insider Trading Activity." Journal of Finance 36 (September 1981). Reprinted by permis- sion of the publisher Blackwell Publishing, Inc. cumulative abnormal return, % 36 32 28 24 20 16 8 4 0 4 8 12 135-120 -105-90 -75 -60-45-30-15 0 15 30 Days relative to announcement date