Thats the enlarged version of the same picture posted recently.
The change of numbering occured late 2004, just as the 44th Division finished. The PLAAF decided to change its numbering system.
The old system goes like this.
1. First and fourth digit - 1 = Division number
if the division number is less than 10, it is 1st and 4th digit - 11.
Thus 4xx5x = 44th Div but
1xx2x = 1st Div.
2. 2nd digit is the last digit of the regimental number. If the regimental number is the 16th Regiment for example, the number is 6. (Note this is not true of the regiment below 9).
Thus the 6th, 16th, 26th and 36th Regiments are numbered 6. The 131st Regiment of the 44th Division has "1" at its number.
3. The 3rd and 5th number represents the plane's serial number in the regiment. There are 24 to 32 aircraft per regiment, so the numbers are 01 to 32.
4. The colors are either red for old planes, blue on the new planes.
NEW SYSTEM:
1. 1st and 4th digit - 11 = Division number. (So they simplified it).
2. The 2nd digit no longer represents the actual regiment number, but who is the lead regiment for that division. There is 0, 1, 2 because each division has 3 regiments on the average. Except for the ones with the Q-5s, they go all the way to 3. The regiment that gets a "0" is the lead regiment, the top honcho. Second fiddle gets the "1" and the last gets the "2".
3. The 3rd and the 5th digit now represents on the plane's serial number as of the division. Not regiment. A division has 3 regiments, and that can mean anything from 60 to 120 planes total.
If a division has 90 planes for example, the first regiment of that division should be 01 to 29. The second regiment should be 30 to 59. The third regiment should be 60 to 89.
4. The letterings is now marked orange.
For example, in the 1st Division,
1st Regiment gets J-8F. The old number is 10x2x.
2nd Regiment gets J-11. The old number is 11x2x.
3rd Regiment gets J-7E. 12x2x.
When it was reorganized, the 1st regiment now gets 11x2x. But the xx numbers are fairly low. The 2nd Regiments gets 10x2x showing the superior priority the J-11 has even of the J-8F, but the xx is fairly high, denoting a midrange number and regimental position.
In the 18th Division, the Su-30MKKs get the 0 number, 20x9x, but the JH-7A get the 1 number, 21x9x. The Q-5s gets the 2 number.
In the 28th Division, the JH-7A gets the 0 number, 30x9x, but the Q-5s get 31x9x to 33x9x. Again, this shows who leads and who follows.
Here is something neat. In the 3rd Division, the 7th Regiment is the one that got the Su-30MKKs, but recent pics show they now have numbers 11x4x. xx is from 01 to 19. For example, 11140.
But the 9th Regiment, which got the J-10s, is now 10x4x. xx is from 50 to high 70s. (the 8th Regiment should be from 20 to 50). The "0" status in the 2nd digit suggests that the J-10s have the **lead** status even over the Su-30MKKs. That is quite significant, especially the 3rd Division happens to be the most elite formation in the PLAAF (or at least the most favored by the Shanghai clique).
So if you digest all this, this explains the change of the numbering mode in the 44th.
However, the 131st Regiment should have numbers from high 20s to the fifties. Clearly a number in the 7x range puts it in the 132nd Regiment. As a note from the J-10 video, the 131st Regiment kept the numbers on the side of their aircraft like No. 26, while transitioning to the new orange unit numbering. But these new 44th division planes do not have the unit numbers on the side.
As a note, there is also a picture of J-10 50150, still in blue letters, but suggesting the new number mode has taken place, as being taken in late 2004. Either way, under the old system, the 2nd digit 0 would have been the 130th Regiment, and under the new system, the 3rd and 5th digit 10 would also have put the plane under the 130th Regiment. All three, 130th, 131st and 132nd, are from the 44th Division.