Rambo for NES undiscovered secret

There is an undiscovered hidden secret inside. See the ammo values in the current video? If you manage to collect exactly 2 throwing knifes, 3 arrows, 4 exploding arrows, 5 machine gun rounds and 6 grenades somehow being at the EXP level 1 (possibility is VERY low), all ammo and health will refill to 99/9 permanently. The main problem is this need EXP level be exactly 1, but this is only 320 EXP points until the level 2, so you may not collect all items as needed before that. Another option is to reach all ammo amounth to 77 77 77 77, and you'll give the same 99/9. But this time, if you already have all 77's, why you need all 99's? lol