The dialog specifies project Combine Stocks options.
This option allows combining several stocks into one in cases when some parts are longer than any stocks. Newly combined stock will have an ID that is combination of stock IDs delimited by a semicolon (;). For example, stocks "A1" and "A2" combined got an ID "A1;A2".
This enables the combining stock functionality.
Some hardware or logistic limitations can require usage of only few different stocks length. In the worst case scenario only one length is allowed. This option accounts for such requirements and specify how many different stock length can combined into one stock.
Note: This option is not about number of stocks, it is number of different stock lengths. For example, you can have selected 1 stock length and 1DCutX could combine several such stocks to accomodate a part.
If you have specified any waste stocks (remnants from previous cuts) you can combine them to actual stocks by selecting this option. Unchecked option will use strictly actual stocks or waste ones without mixing them.