Why did Hashem saw "you saw well"?
Radak: He saw a branch without leaves or flowers. He contemplated the vision, and understood that it is almond wood. Had he seen it with leaves and flowers, it would be simple!
Malbim (11): The hand that touched his mouth pictured in Yirmeyah's imagination an image and parable for the Nevu'ah - "uv'Yad ha'Nevi'im Adameh" (Hoshe'a 12:11). Yirmeyah said that it is as if a Makel Shaked illustrates the hand that touched him.
Malbim #1: (a) He called it a Makel, and not a Mateh, for sometimes Mateh is a support and position of authority. It is honor for the one who bears it. Makel is not for honor; it is for beating. So the Babylonians are a stick of bullies to afflict sinners, not a staff of honor or support. (b) He saw that it is Shaked, i.e. bearing fruits at this moment, showing the great rapidity to bear fruits. Refer to 1:11:3:1-2.
Malbim #2: You saw that I intend to fulfill it quickly for the good. Refer to 1:12:2:1*.
What is the meaning of "Shaked Ani Al Davarai La'asoso"?
Malbim: Carrying out [the prophecy] is connected to the words; it will be done quickly 1 .
Malbim: This was for the good, to exile Yisrael [two years] before [852 years, the Gematriya of] "v'Noshantem ba'Aretz" (Devarim 4:25), lest be fulfilled "Avod Tovedun" (4:26).
