According to ICAO 4444, a change of speed or level should be written in item 15 of the flight plan according to these rules:
Change of speed or level (maximum 21 characters)
The point at which a change of speed (5% TAS or 0.01 Mach or more) or a change of level is planned, expressed exactly as in (2) above, followed by an oblique stroke and both the cruising speed and the cruising level, expressed exactly as in (a) and (b) above, without a space between them, even when only one of these quantities will be changed.
Cruise climb (maximum 28 characters)
The letter C followed by an oblique stroke; THEN the point at which cruise climb is planned to start, expressed exactly as in (2) above, followed by an oblique stroke; THEN the speed to be maintained during cruise climb, expressed exactly as in (a) above, followed by the two levels defining the layer to be occupied during cruise climb, each level expressed exactly as in (b) above, or the level above which cruise climb is planned followed by the letters PLUS, without a space between them.
Does it make any difference to write an increase in the flight level instead of writing a cruise climb? Are they different flight maneuvers?