When you have multiple record-triggered flows that are configured to run before the record is saved on the same object, the order of flow execution is unpredictable. This means that you cannot guarantee which flow will run first or last, or how they will affect each other's field updates. Therefore, you should avoid creating multiple before-save flows on the same object and instead consolidate them into one flow if possible.
References: https://help.salesforce.com/s/articleView?id=sf.flow_considerations_recordtriggered_before.
htm&type=5