According to the military symbols standards MIL-STD-2525 and STANAG APP-6 there are two ways to indicate a half company (reduced company). The two options are showcased in the following example layer: https://www.map.army/?ShareID=1001259&UserType=RC-JAWe3Td4
Option 1:
Using Modifier F to show that it is a reduced company:
The Modifier F can be selected in the MSS Symbol Editor:
Option 2:
The two platoons are displayed as individual symbols: