The ornamental design for lace tightening device dial, as shown and described.
1. Lace tightening device dial
1.1: Top
1.2: Bottom
1.3: Back
1.4: Front
1.5: Left
1.6: Right
1.7: Perspective
The dial can be rotated by a user to tension a lace or tension member via the lace tightening device; the lace tightening device can be attached to an article, such as an article of footwear, in order to tighten the article via the tensioned lace or tension member; the portions illustrated by solid lines are the portions for which the claimed design is intended; the broken lines in drawings represent environment that form no part.