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being USA made they will be an SAE thread in imperial size ( different again to the English UNC/UNF threads , but the same diameters )
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If they are US made, they will more likely be UNC/UNF.
( IIRC, SAE is effectively replaced by UNF for "general purpose" bolts like this )
The English ( and us ) use mainly true Whitworth thread for these smaller dia general purpose bolts, and in that case, Whitworth and UNC are "effectively" interchangeable for dia/pitch, but have a different thread angles.
As such, the test board at Bunnings should be able to confirm the thread pitch and dia.
If they are true UNC, then as noted above, they may have a different thread angle to whitworth, and the numbering system for anything less than 1/4" also changes to a "gauge" based nomenclature.
Ref
https://en.wikipedia.org/wiki/Unified_Thread_Standard
ie Below 1/4" the UNC bolt dia is defined by a gauge, not a fractional dia ( like you would see on a Bunnings Blister pack )
So for UNC fasteners, we get 1/4-20, then 12-24, then 10-24, then 8-32.
vs say 1/4, 3/16, 1/8 etc
The specialist suppliers do stock these true UNC sizes, whereas Bunnings etc dont.
( CostLess Bolts in Moorabbin has pretty much all of these sizes in SS, and is where i get most of mine from )
Andrew