USPS barcode generation: what will be value for FNC1 parameter?

We are generating USPS barcode for GS1-128 type in Laravel using package (milon/barcode).

https://i.stack.imgur.com/iXmcl.png

We are passing ~2129214890227410201234566 as input string in which ~212 is FNC1. But USPS support says its invalid FNC1 character. We tried below possible FNC1 characters as well-

()
{FNC1}
<FNC1>
>8
~1
^1
\F
ASCII character GS (ASCII value 29)
<GS>
<F1>
]C1
%
È (ASCII 200 / Alt+0200)
_1
\x1D
VBA- Chr(29) , ~d029
~212
ñ
[@1]
\u00F1

I have tried with Common FNC1 characters as below:

Here is generated barcode image: https://i.stack.imgur.com/XhgPa.jpg`

What is the correct value for the FNC1 field?

via Chebli Mohamed