Here are examples of ARRN in use, to alternatively route a specific number (or range of numbers) within an SPN.  You can only use ARRN with SPNs.  There is no reason that all NPAs and NXXs cannot be changed to SPNs though.

Example in Area code

SPN  1414 <--------We are processing calls to SPN 1414 (Wisconsin Area Code)
FLEN 0
CLTP NONE
RLI  1   <---------RLI 1 routes all calls to 1-414-nnn-nnnn as needed.
ARRN 332 <---------But 332 (within SPN 1414) must be routed differently
ARLI 21  <---------RLI 21 tells how calls to 1-414-332-nnnn should be routed
SDRR ARRN CODES = 1
ITEI NONE

Example in Local Exchange

SPN  651 <---------We are processing calls to 651 (a nearby local exchange)
FLEN 0
CLTP NONE
RLI  5   <---------RLI 5 routes all calls to exchange 651-nnnn as needed.
ARRN 2345 <--------But 2345 (within exchange 651) must be routed differently
ARLI 18  <---------RLI 18 tells how calls to 651-2345 should be routed
SDRR ARRN CODES = 1
ITEI NONE

Example of Drilling Down to Specific Tele Number

SPN  1414 <--------We are processing calls to SPN 1414 (Wisconsin Area Code)
FLEN 0
CLTP NONE
RLI  1   <---------RLI 1 routes all calls to 1-414-nnn-nnnn as needed.
ARRN 7654321 <-----But 7654321 (within SPN 1414) must be routed differently
ARLI 22  <---------RLI 22 tells how calls to 1-414-765-4321 should be routed
SDRR ARRN CODES = 1
ITEI NONE

Example of Multiple ARRNs in one SPN

SPN  1414 <--------We are processing calls to SPN 1414 (Wisconsin Area Code)
FLEN 0
CLTP NONE
RLI  1   <---------RLI 1 routes all calls to 1-414-nnn-nnnn as needed.
ARRN 332 <---------But 332 (within SPN 1414) must be routed differently
ARLI 21  <---------RLI 21 tells how calls to 1-414-332-nnnn should be routed
ARRN 7654321 <-----But 7654321 (within SPN 1414) must be routed differently
ARLI 22  <---------RLI 22 tells how calls to 1-414-765-4321 should be routed

SDRR ARRN CODES = 2
ITEI NONE