Table 1: Number of candidate members of NGC 6530 for each selection method. Panel 1a: stars in the ACIS field; diagonal terms are the total numbers of stars for each method, while off-diagonal terms are those found by two methods simultaneously. Panel 1b: the same representation for the entire WFI field, including the ACIS field (X-ray sources are not reported as there is no additional X-ray information outside the ACIS field). Panels 2a and b: members found exclusively by one method, in the ACIS and WFI fields. Panels 3a and b: members found by any of the Q indices, regardless of X-ray detection, including X-ray sources and excluding them, respectively, in the ACIS and WFI fields.

Breakdown of NGC 6530 members
1a: Common subsets by different methods - ACIS field
	QJHHK	QVIJK	QVIIJ	QBVJK	X-ray
QJHHK	18	12	5	11	12
QVIJK		124	30	108	53
QVIIJ			53	25	8
QBVJK				151	66
X-ray					884
1b: Common subsets by different methods - WFI field
	QJHHK	QVIJK	QVIIJ	QBVJK
QJHHK	33	17	6	14
QVIJK		200	50	163
QVIIJ			102	39
QBVJK				230
2a: Subsets found by only one method - ACIS field
	QJHHK	QVIJK	QVIIJ	QBVJK	X-ray
	3	8	20	26	807
2b: Subsets found by only one method - WFI field
	QJHHK	QVIJK	QVIIJ	QBVJK
	13	20	47	48
3a: Subsets found by many methods - ACIS field
any Q	any Q or X-rays		any Q and no X-rays
196	1020		120
3b: Subsets found by many methods - WFI field
any Q	any Q or X-rays		any Q and no X-rays
333	1157		257