program CANbus interface on fujitsu MB96340 Series with id filtering

Hello everybody,

i'm interested to program a canbus interface on MB96340 Series 
controller with id filtering.
The problem that i found is on a sample that i found by Fujitsu website.
The code of main.c has something different (for my understanding) as 
describe in readme data.
in the readme data, is told:
CAN-Buffer 1 receives IDs #1
CAN-Buffer 2 receives IDs with with MSB (ID28) set
CAN-Buffer 4 receives all other IDs

And in the code we see:
CAN0_SetRxBuffer( 1, 0x0001, 1, 0x1FFFFFFF); // Full CAN
CAN0_SetRxBuffer( 2, 0x07FF, 1, 0x10000000); // Select messages with MSB 
set
CAN0_SetRxBuffer( 4, 0x0000, 1, 0x00000000); // Receive all messages

1) How does it work if i want this ip filtering on MSB (ID28)?
for me is obvious that id should the full one 0x11111111111 (11bits).
but mask here seems to be for the MSB of an extended ID with 29bits...

2) Why on line 1 mask is 0x1FFFFFFF and line 3 mask is 0x00000000 for 
all other ids?

3) how does it works if i want a filtering on frame with the mask on the 
to two last id-bits
Thanks in advanced for interest and help.

Cemoi71