Number of values in calculations

Every part of the calculation will use the full amount of background decimals to produce the final result. For example, a formula of (Area*10)\Retention Time would take the full value of Area of a peak (say 101456.3098109867..etc) multiplied by 10, then divided by Retention Time of that peak (say 2.3456610988 etc) to give a final result. Empower displays a max precision of 14 decimal places for real numbers but Oracle uses 17 digits in the background. Each field is considered to its full value unless you ROUND it in a formula. 

Using your example above...

Custom Field 1 (boolean): GTE(CustomFIeld, 4) --- this will place a 1 if "true" and a 0 if "false"
Custom Field 2 (peak, real): SUM(CustomField1)

This will not tell you which results were summed, but it would tell you that three values were used to generate the sum). 

Custom field 2 would have to be a Result Real CF not a peak one. Presuming you want a result for each injection, then you would have to make CF2 Result, as you cant sum a peak field unless its part of an intersample calculation. So if you wanted the sum over standard injections like S1 S2 etc then your formula is peak real: S%.%..SUM(CF_1) but SUM(CF_1) on its own as a peak cf will give an error message.