Katnut

Per the Ramchal, there is a bit of conflict. In one place, he brings that the world is ruled by Z"A during the entire beginning of the world up to Yetziat Mitzraim, and in another he says that up until Avraham Avinu, it is under A"A. This can be resolved by saying that things were in such concealment that it is as if Z"A weren't year visible in any way.

The period of Ibbur and Yenikah together or referred to in the Ariza"l by the name of Katnut.

Here's the quote from the Ariza"l:

וביאור הענין דע כי בימי עיבור ויניקה אשר עדיין אז נקראים הקטנות של ז"א

Avraham Avinu's Birth to Yetziat Mitzraim: 1948 - 2448 = 500 Years

• The Year After Yetziat Mitzraim until Bayit Rishon: 2449 - 2928 = 479 Years
• Churban Bayit Rishon to Binyan Bayit Sheini: 3338 - 3408 = 70 Years
• Churban Bayit Sheini to Yemot HaMoshiach: 3829 - 5783 = 1954 Years

Total years of Katnut = 3003 Years

Total years without the Ibbur = 3003 - 500 = 2503 Years

Interesting that this number comes up, so close to a multiple of 500 like the years of the Ibbur, but also because the year 2503 (2504 if you add 1) came up in the discussion regarding Yovel from before, as the first year that Am Yisrael counted Shmitah.