what are the $30 charges for?

Just noticed our credit card receives anywhere from one to three $30 separate charges each month in addition to our monthly invoice charge? What are these $30 charges for? It looks like our credit card is charged and then after the fact are noted as a credit on our invoice? Why are the charges happening if they are just going to be added back as a credit? Is this happening to any other clients? Looking at our history it started in June 2021 and occurs monthly with the last $30 charge being on 3/16/22....please help clarify what is going on.

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