"[EDIT: worked out how box 14 on my W-2 was calculated. I assume this is "compensation reported on your W-2"]"
The compensation created by RSUs vesting is: (GROSS number of shares in grant, before shares are withheld for taxes or sold for taxes) x (per share "fair market value" selected by your employer). Your per share basis is the same as the per share fair market value used to calculate the compensation. Box 14 is typically used with RSUs to disclose the compensation included in Box 1 of the W-2.
The per share basis is what you will also use for future sales and there's no need to mention the number of shares in the grant; the latter is all swept up in the W-2 figures.
