Hi PAWEL,
After you mentioned the Bank Number
8064, I can now imagine what you meant by "User Bank": It's about CUSTOM Voices, i.e. Voices in
Expansion Packs.

CUSTOM Voices are user or third-party created Voices in Expansion Packs. A distinction is made between Custom
Normal Voices (MSB=63) and Custom
Drum Voices (MSB=62).
Each Pack in the YEM (Yamaha Expansion Manager) has a specific
LSB number (0 - 127). The YEM always automatically uses the lowest free LSB (but can be changed by the user if desired under "Change Bank Select LSB"). The
first imported or self-created Pack has LSB=0 by default.
Some MIDI programs do not work directly with Bank Select MSB and LSB, but use BANK NUMBERS, which are calculated according to the formula "
banknumber = 128*MSB + LSB".
With the Bank Number
8064 you mentioned, Custom
Normal Voices in the
first installed Expansion Pack are addressed (128*63 + 0 = 8064). Custom
Drum Voices in the
first Pack would have Bank Number
7936 (128*62 + 0).
For voices in further Expansion Packs, their
LSB number must be added to the specified Bank Numbers. E.g. the Bank Numbers for Custom Voices in the Pack with LSB=1 are:
Normal Voices in
second Pack: 128*63 + 1 = 8065
Drum Voices in
second Pack: 128*62 + 1 = 7937
By the way, Voices in Expansion Packs created by YAMAHA usually have
fixed Voice Numbers (MSB and LSB are fixed), i.e. different from MSB 63 and 62. Here, the LSB assigned to the Pack in question by the YEM is irrelevant.
Hope this helps!
Best regards,
Chris