Rocketman123 (quoting NLT):
The land finally enjoyed its Sabbath rest, lying desolate
Except that isn’t what Jeremiah said. That’s from Leviticus 26:34-35. It is clumsy writing, but in addition to the period of nations serving Babylon for 70 years, the reference to Leviticus alludes to the fact that the period from Jerusalem’s destruction until the Jews’ return was 49 years (see full context of Leviticus chapters 25-26).