This is the number of your company's stock option plan. The plan number differs from the grant ID in that your company will have one stock option plan and corresponding plan number but may have many grant IDs, one for each award of stock options. Top

A number assigned to a document that describes the subdivided parcels of land thereon as numbered lots, blocks, or parcels of a lot, block, district lot or section. Plans are numbered in consecutive sequence within each of several land registration districts and are registered in the respective Land Title Office under the name of the Surveyor Gener [..]