I have had a high cost in adf in one day, more than 20 USD.

I have had a high cost in adf in one day, more than 20 USD, why? I handle very little volume of data, I have the data in a blob storage, the files are less than 1MB, they are very small xlsx and csv. I have developed only three very simple pipelines and last January 28 I had a cost of 21 usd. I don't understand why, could someone help me?

thank you very much