An exact blind fitting size is the finished size of the blind including any hardware. For example, for a roller blind, the exact size would be the width including the operating mechanism, the brackets and the bracket covers. The fabric itself would be narrower. And the height would also include the brackets and roller tube. As another example, for Venetian blinds - width would include the full width of slats and headrails. The height would include the headrail and bottom bar. Note it is normal for some blinds including roller blinds and Venetian blinds to be able to extend below the submitted height, since the position when lowered can be fine-tuned by the customer. When you submit an exact blinds size, no deductions will be made to this size during manufacture.