A great chesed that Hashem did for Bnei Yisrael was to count the shibud Mitzrayim from the day Yitzchak was born. Therefore, it wasn’t until 190 years later that the actual physical labor began, meaning Bnei Yisroel was in Egypt for 210 years. The question is, how can this be done? God is exact in everything. A possible answer is that with the birth of Yitzchak the potential of a father sacrificing his son came into the world. This alone is enough pain to cover 190 years. Though we are ultimately redeemed 210 years later from physical work, the 190 years counted as a galus, as a ketz, which in gematria equals 190. We know that Moshiach’s arrival is referred to as ketz, which is a hint that tests and sacrifices count as much as physical pain, and as we endure travails, the time for Moshiach’s arrival can be shortened.