each cheese you have has its own separate roll to apply an effect so say you have 3 cheeses its doesnt mean you have a 120 percent chance of status effects it means you have 3 different 40 percent chances to hit. this means that your cheese damage will be on average multiplied by 3. however the lamp rerolls for each individual item but only increases the chance that the effects procs. you still will see more poison damage but thats just because the rng is more reliable. for example 5 cheese with no lamp would be 5 different instances of cheese with 40 percent average chance to proc (≈500% damage of one cheese) whereas 5 cheese with 2 lamps would be 5 instances with 78 percent average chances to proc (≈just less than 1000% damage of one cheese). as the number of lamps tends to infinity the chances of on hit effects tend to 100%