Absorption is the numbers listed below "Absorption" on the right of the second page of the equipment menu. The numbers are a percent reduction applied to their respective damage type (Physical Absorption reduced Standard damage, all other Absorption have their names correspond with the damage type) after the effects of your Defense. Absorption can be obtained through Armor, Rings, Weapons, and Weapon Skills. Additional sources of Absorption suffer diminishing returns, which can be calculated with the formula below.
Final Absorption = current absorption - [(current absorption × new absorption) ÷ 100] + new absorption
An example is shown below with these circumstances: The player is currently wearing Havel's chest piece (+18.5), they then equip Havel's helm (+6.7).
Final Absorption = 18.5 - [(18.5 × 6.7) ÷ 100] + 6.7
With these circumstances the final result is 23.9605, Dark Souls round the 5 down and your final result in game is 23.960.
- The absorption stats (and the player menu as a whole) are unable to visually update while the "Cannot change equipment at this time" message is on screen.