SF classification uncertainties after leasing use (and other questions)

Hello together, I try to explain my car insurance history chronologically: First own car registered and insured on myself 18 years ago (always TK). Since then, permanently owns cars and TK-insured on me until 2013. The first 8 years always at the DBV, then at the AXA. In 2013 I used the car full cascade offered by BMW in conjunction with a leasing car and was therefore the last 3 years over BMW at the ERGO So I have “real” 15 years of insurance. Now I wanted to insure a new car with the AXA (VK), which tells me however, that I have only one SF8 in both TK and VK. Now it is complicated: 17 years ago I had a self-inflicted accident (at that time approx. 2,500DM damage), which was regulated by the DBV. At the AXA I later had two or three vandalism damages, which I had I am aware of the fact that the 3 years of Ergo are not recognized by AXA. Nevertheless, after 18 years, an SF8 seems to me to be somewhat low? Unfortunately, I also don’t have any documents from the time before the BMW lease, so I can’t understand how the AXA actually classified me until 2013. Can any of you understand the SF8? Thank you very much!