This reference tells the manufacturer: "For any dimension that does not have a specific tolerance listed next to it, use the standard values defined in ISO 2768."

: Specifies general tolerances for linear and angular dimensions (external sizes, internal sizes, radii, and chamfer heights).

By specifying a standard like in a drawing’s title block, designers can avoid cluttering the page with hundreds of individual "±" values, as the workshop will follow the predefined values for that specific class. Structure of the ISO 2768 Standard

On a drawing, you will see a combination like:

A bent bracket with a hole pattern. Drawing: Overall length = 150mm, Threaded hole positions = non-critical. Title block: ISO 2768-c (Coarse). Result:

Modern CAD software (SolidWorks, Inventor, Fusion 360, NX) has built-in tolerance libraries. When you select "ISO 2768-m" from a dropdown, the software automatically applies the correct tables to your 3D model and 2D drawing. Check your software’s documentation (help PDFs are often free).