default; at the time of omission
Used in technical contexts such as programming or settings to indicate a fallback value or state when something is omitted or not specified.
The default for this setting is 'Auto'.
When the argument is omitted, the default value is used.
初期値 means 'initial value' and refers to the starting value before any changes, whereas 省略時 refers specifically to the value used when something is omitted.
Compound of 省略 (omission) and 時 (time), literally 'at the time of omission'.