grade comparisons

I'm trying to do some DYOR on grade comparisons however there must be a different way companies grade their thickness!

Black rock (BLR) released a JORC of the following grade:

Using a cut-off grade of 0.025% U3O8:
Category Tonnes Grade U3O8(%) Pounds U3O8
Indicated 17,910,000 0.057 22,567,741
Inferred 29,898,000 0.057 37,652,173
Total 47,808,000 0.057 60,219,914

Or using a 0.075% U3O8 cut-off grade:
Category Tonnes Grade U3O8(%) Pounds U3O8
Indicated 4,406,000 0.111 10,781,688
Inferred 6,387,000 0.121 16,982,818
Total 10,793,000 0.117 27,764,506

What is the difference with using a different cut of grade?

Secondly PEN grade seems to be using a different measurement?

An Indicated Resource of 4.0Mlbs eU3O8 grading 510ppm
An Inferred Resource of 11.1Mlbs eU3O8 grading 507ppm

Is BLR grades superior or inferior to ours? These are the things we need to be talking about! Gus did say after drilling the roll fronts our grade will be higher!