Amsterdam to Belgium and Back to Amsterdam

I have confidence in my driving skills, so I only purchased basic insurance. However, I was required to pay a fee of €143.37 when picking up the car. The staff explicitly told me this was a deposit. When I mentioned that other car rental companies usually require a deposit of €1000-1500, the staff said: 'We only require this much.' During the entire rental period, there were no accidents. However, I received an email stating that there was a scratch on the bumper, with a repair estimate of €170. If I accept the charge, they will deduct it from the deposit, and the rest will be waived. If not, they will charge the full repair cost later. This whole situation is filled with doubts, it seems that this rental company sets a trap for unsuspecting customers. Moreover, the said scratch is on the black plastic part of the bumper, and they did not provide a complete picture of the front of the car, only general and paint-damage photographs as we usually take.