XRP and XLM utilize tags and memos respectively to determine which wallet a transaction should be deposited into.
For XRP: Newton does not maintain a unique deposit address for each user, and a tag is required for all XRP deposits.
For XLM: Newton maintains a unique deposit address for each user, so they are not required when funding your account with XLM.
Many other exchanges utilize one or two deposit addresses for these currencies across their entire user base, and thus require the extra information to determine who the deposit is meant for. To withdraw XRP or XLM from Newton to another wallet, first verify whether or not the destination address has a tag or memo. If the destination address does not require a tag or memo, then you can enter any number. If the destination address does require one, please ensure you have entered the correct tag or memo!