せいぜい
At most, at best onlymachine translation
Formationせいぜい + quantity / degree
せいぜい is an adverb placed before a number or degree to say "that is the MAXIMUM — and that maximum isn't much": at most, at best only. It always carries a belittling nuance, making the number that follows sound distinctly small.
Position: right before the quantity expression — せいぜい五百円 (five hundred yen at most), せいぜい十分 (ten minutes at most). Since it's a ceiling estimate, it very often pairs with 〜ぐらい／〜くらい or ends the sentence with だろう.
Distinguishing it: 〜にすぎない ("is nothing more than") downplays the importance of the whole matter, while せいぜい only caps the number. せいぜい also has another use, as a condescending word of encouragement: せいぜい頑張ってください ("do your best, then") — it sounds a bit patronizing; at N3 you only need to recognize it, not use it.
Examples
昼ご飯に使えるのは、せいぜい五百円だ。
The most I can spend on lunch is five hundred yen.
ここから駅まで、歩いてもせいぜい十分ぐらいです。
From here to the station it's at most about ten minutes on foot.
彼は忙しいから、来られてもせいぜい一時間だろう。
He's busy, so even if he can come, it'll be an hour at most.