The initial allocation is the Model Account Equity at moment you turn on subscription (multiplied by AutoTrade Scaling).
For example, let's imagine you start AutoTrading a strategy on July 10. You choose 200% scaling. On July 10, the Model Account for that strategy showed equity of $150,000. (i.e. The point on the equity chart at July 10). Your "Starting Allocation" would be $300,000.
Now, let's say the strategy performed well. On August 30, the Model Account chart showed $175,000. Now your "Total" allocation would be $175,000 x 200% = $350,000.
So, in essence, allocation answers the question: "How much nominal capital have I allocated to this strategy?"