“The full tube was for an animal of 2,500 lbs. The gradations were by 250 lbs. I assume that a lb of horse is equivalent to a lb of person!?”
No, a person is not a horse and absorbed and digest things at a different rate.
Another Example: What level is safe for human could be dangerous for a dog.
You should find a doctor to tell you the correct dose. There are doctors that do telemedicine that will give you a prescription for humans.