The MoM rate (the amount prices increased in July) was zero (down from 1.3% in June), not -0.5%, meaning that prices stayed the same. If it had been -0.5%, that would have meant prices decreased in July by half a percent. The YoY rate is what fell by 0.6% (not 0.5% like I thought), meaning that prices had risen a total of 8.5% since July 2021, a decrease from 9.1% in June (vs. June 2021).
I think it was MoM rate that was -0.5%, YoY rate was still above 8%.