Commercial Fixed Wing
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 44; Flight Crew Total 19650; Flight Crew Type 6000
Confusion; Troubleshooting; Communication Breakdown
Deviation - Speed All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; No Specific Anomaly Occurred Unwanted Situation
Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented
Chart Or Publication
We were flying the VALLY2 SID out of MIA.  The SID note states; 'SPEED RESTRICTION...Turbojet aircraft accelerate to 250 knots; if unable; advise ATC.' I was the PF (Pilot Flying) and at 10;000 feet; I asked the Captain for Economy Climb.  We accelerated to ECON CLB.  Shortly after reaching this speed; ATC instructed us to fly 250 knots and stated something like...Aircraft X; maintain 250 knots; Center will give you a higher speed; you've already accelerated.  (Not verbatim; I cannot remember the exact phraseology). It gave us the impression that we missed a published speed restriction.  After rereading the SID note; we are both confident that this is not a speed restriction.  We are also confident that we did not miss an ATC assigned speed restriction. If however our interpretation of this SID note is incorrect; it is not written as it should be. The Jeppesen Chart Legends publication has a section written about speed restrictions.  It clearly states that 'speed restrictions vary widely within individual procedures.' If we unintentionally violated a speed restriction in this case; perhaps this 'wide variation' in depicted speed restrictions needs to be better address from a human factors perspective; since the VALLY2 SID does not clearly depict a 250 knot speed restriction with terminology such as 'maintain 250 until advised by ATC' or 'do not exceed 250 knots etc.
Air carrier First Officer reported confusion with the '250 Knot' wording on the SID.