It is important not to confuse the NLGI number of a grease which is a measure of the worked penetration at 25°C with the viscosity of the base oil contained in grease. Worked penetration measures the hardness or consistency of the soap medium containing the lubricant, whereas viscosity measures the resistance to flow of the base oil contained in the grease thickener.
Depending on the application and operational requirements, it is possible to get an NLGI 00 grease with a kinematic viscosity of 460 cSt at 40°C as in your case, or an NLGI grade 3 grease with a base oil viscosity of 15 cSt at 40°C. Generally, the NLGI requirements are selected based on speed and low temperature pumpability requirements while the base oil viscosity is selected for the load that has to be carried.