Blaze B810 Clearances
The dimensions shown in the B810 Clearances represent the minimum clearance to combustible materials, ie mantle-piece, when installed in a non-combustible fireplace refer to AS/NZS 2918 Clause 3.4.2
Blaze B810 Hearth
The dimensions given in the installation diagram are the minimum required for the floor protector. It may be desirable, eg for aesthetic reasons for the floor protector to be larger than these minimum dimensions. The floor protector shall be constructed of 22.5mm minimum thick fibre cement sheet. It may be laid directly on the combustible floor.
For more details and variations on floor protectors refer to AS/NZS 2918:2001 Clause 2.2, 3.3.1 and 3.3.2