A scale of 1:1 means the dimensions in your drawing match those of the part you want. Draw a 100 mm wide part at 100 mm. Supply the production version in millimetres.
Units and scale are different
A drawing can use millimetres while still being scaled down. Conversely, a shape may have the correct proportions but be saved in inches. Measure a known dimension rather than checking the unit name alone.
An imported logo may use pixels, points or other units. Set its width deliberately before creating the production version.
Choose a measurement you can recognise
Use an overall width, hole spacing or circle diameter. Check it in the source file, the export and the portal. This helps you identify where a scale change occurred.
Do not add a dimension line to the laser file, since it may be imported as a production path. Record the measurement separately or use your program's measuring tool.
The artboard is not the available sheet
A large artboard does not automatically enlarge your part. Extra objects far outside the design can affect its measured bounds. Remove them and check the available sheet size for your chosen material.
Correcting a mismatch
If the uploaded dimensions are wrong, check the source and export units first. Scaling in the portal also changes holes, slots and engravings, so check those again. An overall dimension alone is not a complete fit check.
For CAD files, read about DXF export. The drawing guide covers the other file requirements.