Electrical sheets carry a lighting fixture schedule. Plumbing sheets carry a plumbing fixture schedule. The tag on the plan, such as a type letter, matches a row in the schedule.
Example: an electrician counts each fixture tag on the lighting plans. The schedule gives the catalog number, lamp, voltage and mounting for each type.
Count by tag, then price by schedule row. Check that every tag on the plans has a row and that every row appears on the plans. Read the notes under the schedule. They often add items such as emergency battery packs.