More ways to see it:
If you are tuning to DAd, it'd be from low to high : D3, A3, d4.
https://dulcimer-noter-drone.blogspot.com/2010/12/what-notes-do-i-tune-my-strings-to.html
On a standard 88 key piano, middle C is C4. Middle C has a frequency of 261.63 Hz. Yamaha uses C3 because that corresponds to MIDI note 60.When the note is pressed, you are actually playing a frequency of 261.63 Hz. If you set your tuner to A=440 Hz. As Dusty says, the D is below middle C, A below middle C, and d above middle C if you tune DAd.
Ken
"The dulcimer sings a sweet song."
Perhaps this page from Get Tuned will help. Your low D is the D below middle C and your middle string is tuned to the A below middle C.
