I’m not sure where these 2 Damage Points do come from.
When you amputate you should roll Medicine and depending on roll outcome apply Critical Injury #61 as Lethal (all typical consequences) or non-lethal.
See both listed below.
In some results on the Walker Attack table, you must amputate a body part to survive. The person who is cutting off a piece of you must make a Medicine roll. Both of you take one point of stress. Whether the roll is successful or not, you take the critical injury “severed limb” (#61, page 69). But if the Medicine roll is successful, the injury is not lethal, as indicated in the table. Should the skill roll fail, the injury is lethal and handled as normal.
LETHAL INJURIES: Some critical injuries are lethal, mean- ing they will kill you after a certain amount of time unless you are stabilized before it runs out. The time limit is decided by rolling a die, indicating the number of minutes, hours, or days you have left, as specified for each injury. The GM makes this roll secretly.
If someone attempts to stabilize you and succeeds at a roll for Medicine before the time limit runs out, you survive. The time limit also states what kind of medical equipment is necessary to help you, either basic (B) or advanced (A); advanced can be used in both cases. With- out the right equipment, there is nothing to be done.
Stabilizing a lethal critical injury takes time and demands that you are in a safe place with enough food and water. Only one attempt can be made each day.