Not very many, it took 18 months following the law's passage to get the rules in place. According to the former INS:
"During this period, INS issued citations only against first-time offenders who had already received an educational visit from the INS and imposed fines only against employers who continued to break the law after receiving both an educational visit and a citation. At the end of this period, INS had issued 2,322 citations and 107 Notices of Intent to Fine, totaling $448,450."
After Reagan left Bush 1 did continue with enforcement for a while but due to enormous pressure from businesses backed off. We've had no real enforcement since.
Thank you for the information.