The apostle Paul wrote the following in his epistle to the church at Philippi.

Php 2:5  Let this mind be in you which was also in Christ Jesus,
Php 2:6  who, being in the form of God, did not consider it robbery [harpagmos] to be equal with God,
Php 2:7  but made Himself of no reputation, taking the form of a bondservant, and coming in the likeness of men.

Many literal translations of the Bible have something very similar to the NKJV above.  Such a translation is not easily understood.  Numerous other translations have something similar to the NASB, which is a little better but still not clear.

Php 2:6  who, although He existed in the form of God, did not regard equality with God a thing to be grasped [harpagmos],

The Greek word translated “robbery” is harpagmos and it can mean robbery or plunder.  However, Thayer’s Greek Definitions also gives a meaning of “a thing to be seized upon or to be held fast, retained”.  This meaning makes the verse more easily understood.  Jesus did not consider his equality with God something to be retained.  He was willing for a season to become a man.  Thus the verse could be translated and easily understood as follows.

Php 2:6  who, being in the form of God, did not consider equality with God a thing to be held fast to [harpagmos],

Conclusion

Jesus “did not consider it robbery to be equal to God” means He “did not consider equality with God something to be held fast to”.  In other words, in true humility He was willing to become human for a season.