hello bro, charging practices helps to maintain the gradual reduce of battery health. we cannot freeze the battery health at 100% for long time. as we use the device battery health will reduce slowly. if usage is high then it reduces bit faster. just to avoid fast reduce we use the charging practice to help battery maintain its level.
so in your case calculate from month of first use. 8 months usage and 2% reduce is normal. you will see few more percentage reduce in upcoming months. that is normal dont worry. continue with the charging practice. that will help.