LSB is least significant byte. 'LSB first' would be what is called little-endian, which is how the value is stored in memory. The LSB is stored in the lower (of the two) memory address, the MSB is stored at the next address. With 2 bytes, you are dealing with an Integer. So, if the Integer contained x15F3, the 2 bytes would be stored in memory as F3 15.

It apppears that your task is to write an Integer followed by a string.