The SB has only a little more than the starting stack, and you have him covered slightly, and it's not the bubble yet, so you are only moderately risk-averse against him. You are getting some odds from the blinds. So, the ICM says that you need 53.08% equity against the SB's range to call. A4o has 56.7% equity against a random hand, and is close to 50% against a top 50% hand (a useful value to remember), so I would expect A4o to have enough equity against about a 70% range. SNG Wizard's 60% range is better as a calling range than a pushing range, which may be why there is a slight discrepancy.
Here is some output from my program ICM Explorer:
Fold: 2380 chips, 0.1829, SD: $16.87
Win: 4715 chips, 0.3076
Lose: 445 chips, 0.0418
Tie: 2580 chips, 0.195
Equity needed: 53.08%
Chip odds: 45.32%
Risk premium: 7.76%
Chips gained by marginal call: 331.38.
Ties count as 57.62% of a win.
SD of marginal call: $17.67.