If you round $4,329.97, $452.28, and $279.34 you would get $4,000, $500, and $300. If you add $452.28 (rounded to $500) twice to $4,329.97 (rounded to $4,000) then you would get $5,234.56 which you would round to $5,000. Then when Alexa withdrawals $279.34 (rounded to $300), you subtract $279.34 from $5,234.56 (rounded to $5,000) and you get $4,955.22 which would be rounded up to $5,000. This proves that Alexa's estimate was reasonable.
