This summary is not the rule. The rule text controls.
Here's a plain English summary of this rule:
If someone files a garnishment action against you as a garnishee, there are certain things that can't be used as grounds for a judgment against you. A court can't order you to pay money in a garnishment case just because you signed, accepted, or guaranteed a check, promissory note, or similar financial document.
The same protection applies if you're holding money tied to a claim that isn't based on a contract and where the amount owed hasn't been officially set yet. In other words, if the debt is disputed or unclear and doesn't come from a contract, that alone isn't enough to force a garnishment judgment.
Finally, if you're holding money or property that the law says is exempt from garnishment (or money that came from selling exempt property), a court can't use that as the basis for a judgment either. This rule exists to protect garnishees from being unfairly forced to pay out money in situations where the law says that money should be off limits or where the debt itself is too uncertain to enforce.