sudo-code
#ie:
#Read and save serial number to database.
#Table: | prefix | number | stamp | (index the stamp)

#Now build for the display... 

"SELECT DISTINCT number FROM table ORDER BY stamp LIMIT 20"
etc;

## Now get prefixes associated with those numbers.
## Remember the other serial numbers (prefixes) may be received at any time in the past.
for (each number) {
  "SELECT prefix FROM table WHERE number=$_"
  fetch() 1 to 4 elements per number {
    ## build, in a string, array, or hash for display
    "number XX XX XX XX"
  }
}