Level 4 Schedule example

I’m not sure if there’s a standard approach to numbering or describing levels of detail, but we use;

Level 1; Top level milestones - 1 A4 sheet for the project
Level 2; Phase level planning - 1 A4/A3 sheet per work area - Gives focus to phase lengths (planning, execution etc)
Level 3; Execution strategy - a few A4/A3 sheets per work area - details overall approach to the execution of the works
Level 4; Activity detail - 20k+ activities - 1 activity per man-shift
Level 5; MH calculation lines that drive the activities

This is used for Oil and Gas maintainence turnarounds, traditional building work I would say may lack level 5 completely and be of the order of one man-month per activity at level 4 (depends on your reporting period.)

I expect, though, that what your employer is demanding is one level of detail deeper than whatever you are currently providing. It is a common technique to scheudule the next 2-4 months work in a deeper level of detail than your overall plan, in your case perhaps you start the project with a level 3 plan for the whole project before you start (at tender perhaps) and then to schedule at Level 4 the works coming in the next 3 months. The term for this is "rolling wave" planning