Those numbers are the true byte values of 512MB and 128MB respectively.

Some people have found VFP never benefits from more than 512MB RAM no matter how much is actually installed in the system or how large the data tables e.g. http://fox.wikis.com/wc.dll?Wiki~sys3050~WIN_COM_API . There was further discussion here a little while ago, at least 1 user hasn't found any benefit going over 128MB. Thread#1623614

As a side note, while I think about it personally I'd be inclined to use slightly less than those values - either 4K less (4,096 bytes) or 16K (16,384 bytes). Primarily to avoid a potential internal switch to any sort of internal "large memory mode". Apparently VFP has a lot of old legacy code originally written in the days when RAM was very limited compared to today. This caused some problems, for example the original VFP 3.0 would not start on a machine that had more than 512MB total memory installed. It had to be patched to 3.0b to avoid that issue. One way to avoid that in the interim was to configure Windows NT-based OSs to use just slightly less than 512MB RAM. I don't know if any of that old cruft persists into VFP 8 or 9.

>Thank you Noato.
>
>I just added these 2 commands to the top of my start.prg that loads my environment.
>We'll see what happens...
>
>Can you explain when setting the Foreground and Background buffer memory sizes,
>what the 536870912 and 134217728 numbers mean? (iel, where did they come from?)
>Are these the maximum size memory that can be set?
>
>I have a 32 bit laptop with 4 gigs of memory.
>
>Thanks.
>Cyrus
>
>
>>>This has been happening more and more.
>>>Couple years ago it happened once a month, not it happens 10 times a day.
>>>I have to reboot to even be able to work a few minutes in VFP.
>>>
>>>Here is how it starts;
>>>
>>>- I start VFP, and it is sitting on the Command Window. Doing nothing.
>>>- I work on another application like my email or IE, ...
>>>- Then after few minutes I get this error you see on the Screen-Shot.
>>>
>>>What could be causing this? Help would be very much appreciated..
>>>
>>>Thanks
>>
>>What happens if you repeat the test, but enter these commands immediately after opening VFP?
>>=SYS(3050, 1,536870912)
>>=SYS(3050, 2,134217728)