ありがとうございます。車の国境越えの時みたいに当日国境で直接$6払うのだとばかり思っていました。アムトラックのWEBにあったのですね。Up to 7 Daysだったので7日前を切らないとだめみたいですね。あと2ヶ月あるので覚えておかないとです。助かりました!
あとは当日2時間とか遅れない事を願うばかりです。
Appear at a port of entry within seven days of completing this online application.
Q: What happens if I do not appear at a port of entry within seven days?
A: If you do not appear at the border within seven days, your provisional I-94 will expire, and you will be required to reapply and pay the fee again. There are no refunds if the I-94 is not issued within the seven-day period.
Non-U.S. citizens of other countries entering the United States must also apply for the CBP I-94 Arrival Record; this may be applied for and the U.S. $6 fee pre-paid by visiting the U.S. Customs website (i94.cbp.dhs.gov) up to seven days prior to entry date. If the I-94 is applied for at the time of travel the fee must be paid in U.S. currency