Towards the end of the haggadah, there is a paragraph discussing how many makkos there were at yam suf:
רבי יוסי הגלילי אומר- מנין אתה אומר שלקו המצרים במצרים עשר מכות ועל הים לקו חמישים מכות? במצרים מה הוא אומר "ויאמרו החרטמים אל פרעה אצבע אלהים היא". ועל הים מה הוא אומר "וירא ישראל את היד הגדלה אשר עשה יי במצרים וייראו העם את יי ויאמינו ביי ובמשה עבדו". כמה לקו באצבע- עשר מכות. אמור מעתה, במצרים לקו עשר מכות ועל הים לקו חמישים מכות." Rabbi Yosi HaGlili says: From where do we know that the Egyptians were punished with ten plagues in Egypt and fifty at the sea? In Egypt what does it say "The magicians said to Pharaoh 'It is the finger of God'". And what does it say by the sea "The Israelites saw the great hand which God did in Egypt, and the nation feared God and believed in God and Moshe, his servent." How much were they punished with a runner-up 10 plagues. From here you can say, in Egypt they were punished with ten plagues and on the sea with fifty.
(Translation by me)
This logic seems very simple, but there is one problem: a "hand of God" is mentioned a few times in regard to the plagues as well! For example: (Shemos 7:14)
ונתתי את ידי במצרים I put my hand in Egypt (Shemos 13:9) ביד חזקה הוציאך He took you out with a strong hand And even by the plague of pestilence itself it says (Shemos 9:3) הנה יד יי הויה במקנך... Behold God's hand is against your cattle...
So how can Rabbi Yosi HaGlili say that the plagues in Egypt were only a "finger" if the above three Pesukim say they were a "hand"?