What is the length field in SHA-512 padding? If I am using SHA-512 on a message and need to determine the padding field and length field, how do I determine the length field?  I think I understand the padding, but not the length field.

For instance, if I have a 1919-bit message the padding field would be one 1 and zero 0's.  But what would the length field be?  1919?
In $\text{SHA-512}$ the size of the blocks is 1024 bit. The last block must contain:


the rest of data in message (mod 1024).
some filling (padding)
the last 128 bits as length




If the message is 1919 bit length:


Calculate the size of the data in the last block:
$1919 \mod 1024 = 895$
Add the size of length field(128 bit) to the last block size(895 bit), $128 + 895 = 1023$
See that we have to add 1 bit as padding to the last block to became 1024 bit


The answer will be:


size of padding field = 1 bit 
data of padding field = 1 
data of length field = 1919 as an unsigned 128-bit big endian integer 0x0000000000000000000000000000077F