Ammeter time limits - how to understand them
First time I measured a 10A power supply (using a virtually bombproof AVO-8 ) I got a surprise after several minutes when I burnt myself on the test leads! The probes were overheating too, but the meter was made of stronger stuff!

Anyway after that, I'm not surprised to see limitations like that on anything but the most rugged grade of multimeters. At 4 amps I'd keep it down to maybe a minute or so and let it cool off, or if I was making quick measurements I wouldn't worry about it.