LLD macro

[chronicleqq]

Hello! I want to create one data prototype for the parameter of each network card installed in the basket.
OID parameter of the first card
.1.3.6.1.4.1.40989.10.11.12.1.0
second card
.1.3.6.1.4.1.40989.10.16.2.12.1.0
and so on, i.e., in the general case, the type of such
.1.3.6.1.4.1.40989.10.16.x.12.1.0
where X is the index of the installed card, using the detection rule with the type of external verification, I use the Python script to obtain indices of the installed cards and I receive in response to such JSON
{
"Data": [
{
"Board_num": "1"
}
{
"Board_num": "9"
}
{
"Board_num": "20"
}
]
}
After which I set LLD macro with the name {#board_num} and the value of $ .data[*]. Board_num
After I create a prototype of data with the SNMP agent, where I use the Number key. [{#BOARD_NUM}] and OID .1.3.6.1.4.1.40989.10.16. {#Board_num} .12.1.0

But after applying the template, I get the error
Cannot Create item error: item with the same key "number. [#Board_num}]" Alread Exists.
Cannot Create item: Item with the Same Key "Number. [#Board_num}]" Already Exists.
Cannot Create item: Item with the Same Key "Number. [#Board_num}]" Already Exists.
3 times
Tell me what I am doing wrong and when do I eventually create a prototype of the element for three cards?