What is wrong with my dipstick?

[LFY]

Hello dear members,
Please read my story and tell me what is wrong with my dipstick.

Recently, I had a problem with checking my oil level. The story begins about 7 months ago when I drained engine oil and poured fresh oil into the engine.
The manual says oil capacity of my car is 4.25 Liters. I usually let the oil drain for about an hour and then tighten oil drain plug and pour about 4.2L of fresh oil.
I have done this for several times and it has been quite successful because I always see the oil level on the MAX mark on the dipstick.

However, this time, an annoying problem happened. After changing the oil, I drove my car and checked the oil level the day after that. I noticed the oil level is a little below Max mark (despite pouring 4.2L of oil!!). I added about 100 cc of oil to compensate for it. I drove my car again and checked the level and it was still below Max mark! I added another 100 cc to bring it up to the Max mark. I drove it again and checked the oil and to my surprise it was still below Max mark!!!!! I decided to add another 100 cc of oil and then finally I could reach the Max mark! So, I poured 4.2L of oil + 3 x 100 to make it FULL. 4.2 + 0.3 = 4.5L (this is 250 cc more than what the manual says!)

I checked the oil later and it was full!! I was happy that the problem was finally solved and drove the car for a few weeks. One day, I checked the oil level and guess what I saw?! It was ABOVE the Max mark! I was so angry that I didn't know what to do! I sucked the excessive oil with a narrow hose and a syringe!

Now, my question is that why the dipstick didn't show the correct oil level at the beginning and made me to add oil more than enough and end up with an overfilled engine? Why did it take about 2 months for the dipstick to show me the correct level? I don't understand!

[GiveMeABreak]

It is important that you check the oil on level ground and only after the engine has been switched off for at least 15 minutes. If you don't, you'll have oil in the system that has not returned to the sump and this will give a lower level reading than it actually is - and can increase your risk of over-filling it if you keep topping it up prior to waiting.