وَالْبَلْخِيُّ: أَنَّهُ لَا يَقْدِرُ عَلَى مِثْلِ مَقْدُورِ الْعَبْدِ
Al-Balkhī is reported to deny God's power over the like of what is within a servant's power.
A maqdūr is an object of power. “An act like the servant’s act” can refer to a possible act of the same kind, rather than necessarily the identical individual occurrence.
The debate concerns whether an act's being within creaturely ability excludes that kind of act from divine power. The reply distinguishes possibility of the act from the particular manner of its attribution.