Thanks for your message and thanks for the developer report you sent.
Yes, now I see the problem: as I see, the disk drive has letter B:
Generally A: and B: drives were used for floppy disks and fixed disk drives usually have letters starting from C:
Because of this, Hard Disk Sentinel displays the disk drives from C: - Z: only in the drive thresholds menu, this is why the B: drive does not appear there (even if it's a fixed hard disk drive).
I'll examine and make the required change, so then the following version may display B: drive there too (if it's a hard disk drive).
If possible, I'd recommend to try to assign a different drive letter for the new hard disk drive in the range C: - Z: so then it would be surely listed.
Thanks for the image. Yes, as I tried to write, the % value in the e-mail header is NOT related to capacity in any ways.
It shows the lowest health of all drives, to quickly indicate the health value and possible change.
As your SSD has 91% health (due to normal wearout), the e-mail subject shows 91%.
This is not affected by the capacity of the new drive in any ways.