Thanks for your help.
Right, 100 would be the batch size and I have 4 classes.
A sample tensor consists of 224 values.
This is how a piece of the dataset looks like (first measurement sample, then label):
dataset[5]

(tensor([[0.0681, 0.0647, 0.0697, 0.0680, 0.0632, 0.0590, 0.0717, 0.0640, 0.0558,
          0.0673, 0.0649, 0.0675, 0.0678, 0.0717, 0.0726, 0.0713, 0.0720, 0.0757,
          0.0756, 0.0744, 0.0744, 0.0760, 0.0777, 0.0797, 0.0760, 0.0781, 0.0758,
          0.0759, 0.0768, 0.0758, 0.0760, 0.0744, 0.0757, 0.0744, 0.0754, 0.0774,
          0.0777, 0.0788, 0.0829, 0.0857, 0.0875, 0.0942, 0.1035, 0.1125, 0.1204,
          0.1349, 0.1482, 0.1601, 0.1754, 0.1912, 0.2024, 0.2140, 0.2218, 0.2294,
          0.2344, 0.2405, 0.2447, 0.2486, 0.2535, 0.2542, 0.2544, 0.2568, 0.2554,
          0.2477, 0.2405, 0.2350, 0.2305, 0.2221, 0.2132, 0.2095, 0.2054, 0.2022,
          0.1978, 0.1955, 0.1899, 0.1882, 0.1892, 0.1882, 0.1846, 0.1804, 0.1777,
          0.1741, 0.1703, 0.1661, 0.1627, 0.1583, 0.1578, 0.1576, 0.1568, 0.1529,
          0.1481, 0.1425, 0.1366, 0.1270, 0.1198, 0.1130, 0.1099, 0.1076, 0.1022,
          0.0994, 0.0946, 0.0880, 0.0840, 0.0820, 0.0815, 0.0802, 0.0827, 0.0880,
          0.0988, 0.1171, 0.1491, 0.1890, 0.2348, 0.2812, 0.3261, 0.3630, 0.3943,
          0.4248, 0.4504, 0.4734, 0.4962, 0.5118, 0.5217, 0.5316, 0.5350, 0.5365,
          0.5429, 0.5515, 0.5720, 0.5907, 0.5909, 0.5929, 0.6001, 0.6017, 0.6039,
          0.6022, 0.6034, 0.6033, 0.5968, 0.5984, 0.5936, 0.5948, 0.5960, 0.5980,
          0.6030, 0.6056, 0.6022, 0.5938, 0.5872, 0.5832, 0.5741, 0.5695, 0.5610,
          0.5634, 0.5688, 0.5707, 0.5690, 0.5678, 0.5646, 0.5563, 0.5579, 0.5532,
          0.5549, 0.5573, 0.5536, 0.5591, 0.5611, 0.5601, 0.5557, 0.5563, 0.5591,
          0.5535, 0.5577, 0.5565, 0.5551, 0.5545, 0.5469, 0.5592, 0.5621, 0.5559,
          0.5560, 0.5592, 0.5609, 0.5594, 0.5594, 0.5601, 0.5568, 0.5478, 0.5518,
          0.5447, 0.5483, 0.5453, 0.5404, 0.5367, 0.5438, 0.5450, 0.5398, 0.5360,
          0.5313, 0.5155, 0.5035, 0.4977, 0.4822, 0.4723, 0.4667, 0.4621, 0.4480,
          0.4449, 0.4368, 0.4308, 0.4343, 0.4166, 0.4172, 0.4014, 0.3871, 0.3612,
          0.3562, 0.3375, 0.3182, 0.2991, 0.3049, 0.2872, 0.2858, 0.2696]]),
 tensor(1.))