The label says "Apple Cider Vinegar (5% acetic acid) 500 mg".
Does one gummy have 25mg of acetic acid or 500mg of acetic acid?
Acetic acid is a component of apple cider vinegar, and the ingredients list claims 5% - typically calculated weight by weight - that's 5 mg acetic acid per 100 mg of apple cider vinegar. @Bob Brown put the answer in a comment above already, 25 mg for one gummy.
The answer from @Regjohn1 completely missed the important 5% bit, and if it was actually 500 mg dry acetic acid per 500 mg apple cider vinegar per gummy, 1) that's legally not apple cider vinegar, and 2) it would be highly hazardous to consume.