From Br Wiki
FLOWSTACK 100 (version 4.3+)
"Integer" is a decimal number that represents the number of calls the flow stack can hold. This number must be greater than 9.
- FlowStack may only be specified in the BRConfig.sys file; it is not valid with the Config command.
- An error message (9003) appears when the flow stack is too small to handle the number of concurrently active GoSubs or functions.
- The flow stack memory area is taken from available user memory.
- The Status Stacks command shows the current stack settings.