Instrument flight time depends on the type of flying a pilot is doing and where he is doing it. Flying for a day VFR operator should not provide much instrument flight time! Some parts of the world because of different weather/climate require more instrument flying than other parts.
As a rule of thumb the instrument flight time of an experienced pilot will be between 5% and 10% of his total time. Anything over this will require some explaining and proper evidence. A resume with more than 15% would probably belong to a Parker Pen pilot and would go straight into the garbage can.
Here's the information from the World's biggest aviation country:
Federal Aviation Regulation Sec. 61.51 - Pilot logbooks.
(g) Logging instrument flight time. (1) A person may log instrument time only for that flight time when the person operates the aircraft solely by reference to instruments under actual or simulated instrument flight conditions.
(2) An authorized instructor may log instrument time when conducting instrument flight instruction in actual instrument flight conditions.
(3) For the purposes of logging instrument time to meet the recent instrument experience requirements of §61.57(c) of this part, the following information must be recorded in the person's logbook --
(i) The location and type of each instrument approach accomplished; and
(ii) The name of the safety pilot, if required.
(4) A flight simulator or approved flight training device may be used by a person to log instrument time, provided an authorized instructor is present during the simulated flight.