Tesla Inc. (TSLA) gave investors a pleasant shock last week: $1.53 billion in free cash flow, or the money left over after paying for new factories and equipment.

As independent analyst Stephen Gordon put it: "The market had braced for a burn of nearly $5 billion."

But Gordon, a Tesla shareholder, says the number needs a closer look. "Two things built that number, and neither is the business suddenly throwing off cash," he wrote in his CanadianSnowmanSays newsletter.

Lower Spending Flattered Cash Flow

The first was spending. Capital spending came in at $4.73 billion, well below the $7.96 billion Bloomberg polled analysts had modeled. That gap helped the Elon Musk-run company report positive free cash flow, but it also means the improvement came partly from spending less than expected.

Electrek's Fred Lambert reached the same conclusion: "The lower spending also flatters this quarter's positive free cash flow."

The $1.9 Billion Catch

The second factor is how long Tesla takes to pay its suppliers. Gordon points out that the company's average supplier payment period rose from 58 days to 66 days.

"Tesla took about eight more days to pay its suppliers, and those eight days were worth roughly $1.9 billion," he wrote.

That estimated $1.9 billion exceeds Tesla's reported free cash flow of $1.53 billion. By holding cash longer before paying suppliers, Tesla can boost quarterly cash flow without generating more cash from its underlying operations.

Gordon also points to other timing boosts, including customer money received in advance. Strip out those effects, and he estimates free cash flow "would have been about negative $1.1 billion, almost exactly July's figure."

The distinction matters because free cash flow can swing with the timing of payments and investments. A positive figure does not necessarily mean the business has become more efficient at generating cash.

What Investors Should Watch

Tesla's reported cash flow was positive, but investors will want to see whether the company can sustain that performance without lower-than-expected capital spending or longer supplier payment periods. Future results will show whether cash generation improves alongside the business or continues to depend on payment timing.

As Gordon put it, "What changed was the timing of the cheques." For Tesla investors, the next test is whether the company can turn a one-quarter cash windfall into a more durable trend.