MTC MAMBA LITE Parallax concerns

So today I was shooting my daystate huntsman regal with a 3-12 MTC mamba lite in sportsmatch mounts. At thirty yards the parallax wheel read 25 yards in focus, and at 50 yards it read 35 yards in focus. Anyone else have this situation. Is the scope defective, are my ageing eyes the problem or is this a byproduct of the price point? It was set at 12 power.
 
Has anything changed or is this your first time using this scope? If it's your first time using this scope I wouldn't worry about it just as long you can clearly focus at 10 yards at 12x and see 200 yards or farther on infinity. All eyes are different and parallax markings aren't always exact so don't worry about it. Keep your receipt someplace safe don't lose it. Warranty only covers original owner with receipt and non transferable.