Beis Shamai asks this since we started off with a whole jug of oil and each night â…› of the oil lasted until the next day when they used 1/7th so his opinion in Gemara is that we should start with 8 candles and count down. This is also how the sacrifices on Sukkot are done in the Beis Hamikdash starting off with the most and counting down one each day. But Beis Hillel says we only add in holiness so we follow Bet Hillel light an additional candle each night.