let A = Array2.init 3 2 (fun i j -> j*3+i+1);;
> A;;
val it : int [,] = [|[|1; 4|]; [|2; 5|]; [|3; 6|]|]

> let S = Array2.sub A 0 0 3 1;;
> S;;
val it : int [,] = [|[|1|]; [|2|]; [|3|]|] // $1 OK

> let S = Array2.sub A 0 1 3 1;;
> S;;
val it : int [,] = [|[|4|]; [|5|]; [|6|]|] // $2 OK

======================================================================

> let A00 = Array2.init_based 0 0 3 2 (fun i j -> j*3+i+1);;
> A00;;
val it : int [,] = [|[|1; 4|]; [|2; 5|]; [|3; 6|]|]

> let S00 = Array2.sub A00 0 0 3 1;;
> S00;;
val it : int [,] = [|[|1|]; [|2|]; [|3|]|] // $3 = $1 OK

> let S00 = Array2.sub A00 0 1 3 1;;
> S00;;
val it : int [,] = [|[|4|]; [|5|]; [|6|]|] // $4 = $2 OK

======================================================================

> let A11 = Array2.init_based 1 1 3 2 (fun i j -> (j-1)*3+i);;
> A11;;
val it : int [,] = [|bound1=1; bound2=1; [|1; 4|]; [|2; 5|]; [|3; 6|]|]

> let S11 = Array2.sub A11 1 1 3 1;;
System.ArgumentException: out of range // $5 ???? BUG?
Parameter name: src1, len1
at Microsoft.FSharp.Collections.Array2.sub[A](A[,] src, Int32 src1, Int32 src2, Int32 len1, Int32 len2)
at <StartupCode$FSI_0073>.$FSI_0073._main()
stopped due to error

> let S11 = Array2.sub A11 1 1 2 1;;
> S11;;
val it : int [,] = [|[|1|]; [|2|]|] // $6 fist and second value of $1 OK but ?

I don't understand error for step $5