Hi Ariel,
Further to Michael's email, you will find that different oil types have different criterias and OEM's will also have a set of maximum limits to the test. For example, hydraulic oils and gear oils have different maximum limits.
For new oil limits, it's best to contact the oil supplier and get the details for each of the 3 sequence in the tests.
In addition, OEM's will also supply their own limits. For example Denison Hydraulic Requirements says that there should be "none" ie no foam for HF-0, HF-1 and HF-2 fluids. GEK turbine oil specs says 50/0 for sequence I, II and III in the test method. AGMA also have their own specs and requirements for gear oils eg AGMA 9005 says 50/0 upto an ISO VG 680 gear oil and 75/10 for ISO VG 1000 and upwards.
Basically, if the test ASTM D892 is performed and there is a persistent foam - you may have a problem depending on how it is effecting the performance of the equipment and safety factors.