Reserved funds (not to be confused with "reserved" funds on the exchange) are funds that were acquired by the bot earlier but are not yet sold . These funds are reserved for this specific trade pair (market) with the intention to sell them there. Note that this is even so when the market is currently not selected!
When funds are reserved by the bot, they should not be withdrawn from the exchange. Also, the bot will not use them as base currency on another market.
The reserved funds can easily be released: Navigate to the dashboard and scroll down to "Accumulated Funds (order history)" and click "RELEASE FUNDS". A list of the original buy orders will be shown. You can select one or more of them to match the total quantity you would like to release and then click "Confirm".
Consider the following example to clarify things further: suppose 0.1 ETH was acquired on Bittrex:BTC-ETH. Then that amount of ETH would be "reserved" on Bittrex:BTC-ETH only. Hence, this amount of ETH would not be available as base currency on, for example, ETH-ADA.
Note: Should you choose to release a part of the ETH from the above example, with the intention to withdraw the ETH from your account, then it is advised to deselect all markets that use ETH as base currency and wait for the next cycle to complete (check the status timestamp on the dashboard). Then withdraw the funds and re-select the deselected markets. Otherwise, the bot would use the ETH on those markets in its next cycle.