Why on NFC subway cards, 4,5,6,7 pages are blocked by F0 00 bytes?

Question

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Why on NFC subway cards, 4,5,6,7 pages are blocked by F0 00 bytes? Here is an example subway ticket dump:
Card UID: 34 24 87 09 FC DC 56
PICC type: MIFARE Ultralight or Ultralight C
Page 0 1 2 3
0 34 24 87 1F
1 09 FC DC 56
2 7F 0B F0 00 <- This entry , responsible for blocking
3 FF FF FF FC
4 45 D9 B8 0A
5 9E E7 9D 00
6 20 15 00 00
7 20 15 00 00
8 20 11 05 00
9 40 00 30 73
10 80 32 59 84
11 20 11 29 C8
12 20 11 05 00
13 40 00 30 73
14 80 32 59 84
15 20 11 29 C8

Answer 1

Because these blocks store ticket data, which is initially forbidden to change.
Some craftsmen have long known how a subway ticket dump is laid out https://xakep.ru/2009/02/06/47074/
There are also ready-made applications for Android phones with NFC modules for reading these same tickets, I think you can find algorithms if you search