The chargeback ratio is disputes divided by approved sales, and most online merchants use it as their main health check. Below 10,000 sales a month it swings too much to trust. One bad week can push a steady business past Visa's 1.5% Excessive threshold (Visa's limit on how many of your sales can be disputed) with no real change in the business.
Merchants who watch the ratio closely refund disputes they could have won, to keep the number down. They also spend expert hours on cases with thin records, because losing would push the ratio up. Both cost margin without improving the business.
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A better measure is expected value for each case: the chance of winning, multiplied by the amount recovered, minus the expert hours needed to fight. Refund the cases where that comes out negative and fight the ones where it comes out positive. Track your win rate by dispute reason (the code on your notice), by the customer's bank, and by disputed amount.
Visa's monitoring programs still look at the ratio. Crossing 1.5% brings $8 per-event fees, can lead your payment company (Stripe, Shopify Payments and the like) to hold back part of your payouts, and triggers a required plan to bring the ratio down.