A 16-digit PIN is printed on a card. The PIN is split into four groups of four digits. The upper, unstained part shows the full PIN: 0691-1702-4355-7630. The lower, stained part has some digits visibl

The full PIN visible on the upper part of the card is 0691-1702-4355-7630. This is a 16-digit PIN, formatted in four groups of four digits.

From the crops, the following parts of the lower PIN are discernible:

• The first two digits are 07.
• A middle section of four digits is 0157.
• The last two digits are 99.

The lower PIN can be represented as: 07XX-XXXX-0157-XX99.

The stain covers:

• The 3rd and 4th digits of the first group (2 digits).
• All 4 digits of the second group (4 digits).
• The 1st and 2nd digits of the fourth group (2 digits). In total, $2 + 4 + 2 = 8$ digits are covered by the stain.

Upon close examination of the stained areas in all provided crops, the black stain is completely opaque. No digits, partial digits, or outlines are discernible underneath the stain. The crops confirm the extent of the stain but do not reveal any hidden information.

The digits covered by the stain are unreadable.