doubt quote symbols

[Stefano_GS]

Good morning.
I have received a drawing of which I attach part of a quotation of which I have difficulty regarding interpretation.
the and in the circle indicates the need for envelope, but I cannot understand what st means in the hexagon

 

[New Rider]

Good morning.
I have received a drawing of which I attach part of a quotation of which I have difficulty regarding interpretation.
the and in the circle indicates the need for envelope, but I cannot understand what st means in the hexagonView attachment 56953

hi, the measurement on the re-design will be statistically controlled. for statistic tolerances. I stop here because I have no compentence in this matter.

Hi.

 

[Stefano_GS]

Thank you very much
I had never seen any indication of that kind