Quality

"B.S." most likely stands for "Bursting Strength". It is the measure of the amount of pressure required to break the resistance of paper or board under pressure.
B.S = (GSM x B.F)/1000
It's unit is Kg/cm²

The crush resistance of a corrugated box refers to its ability to withstand pressure on the flute without getting crushed. This is an important factor to consider when packaging items for transport or storage, as it helps ensure that the contents of the box remain intact and protected.
Box Compression Test (BCT)=k1∗ECT×√h*Z
Where:k1=a constant value of 5.87
h= Corrugated FiberBoard (CFB) thickness (inches)
Z= box perimeter (inches) = 2(L+W)

The amount of load that the box can safely hold.
Stacking Strength = BCT/Safety Factor

The Edge Crush Test (ECT) is a crucial measure of the compressive strength of corrugated board. This test involves subjecting a small segment of the board to compression on its edge between two firm platens or plates that are perpendicular to the direction of the flutes. The test continues until a peak load is established, which provides a measure of the board's ability to withstand crushing forces. The ECT value is widely used in the packaging industry to determine the strength and durability of corrugated boxes and packaging materials.
Formula
ECT For 3 ply= RCT*(Take-up Factor)+ RCT*(Take-up Factor)+ RCT*(Take-up Factor)
For Liner Paper Take-up Factor is 1

ECT For 5 ply= RCT*(Take-up Factor)+ RCT*(Take-up Factor)+ RCT*(Take-up Factor)+ RCT*(Take-up Factor)+ RCT*(Take-up Factor)

Take-up Factor for Flute given bellow;
A- 1.54
B- 2.46
C- 1.43
E- 1.27

FCT stands for Flat Crush Test. In this test, a single-flute corrugated cardboard specimen is loaded perpendicular to its surface and the resistance that the corrugated board presents to the force provides an indication of its behavior during processing and in use.

GSM stands for "Grams per Square Meter". It is a unit of measurement used to determine the weight or thickness of paper, fabric, and other materials. It refers to the weight of the material in grams per one square meter of area. For example, if a paper has a GSM of 80, it means that one square meter of that paper has a weight of 80 grams.
Gram/mtr ²

Is it bursting factor of paper.
B.F= ( B.S x 1000 )/GSM