How to interpret DAT element data export of a hexahedron mesh?


3063 102 3076 3077 
3064 102 3077 3078 
3065 102 3078 3079 
3066 102 3079 3080 
3067 102 3080 3081 378423 204 365672 365711 365712 365673
 ~~~
378424 204 365673 365712 365713 365674 
378425 204 365674 365713 365714 365675 
378426 204 365675 365714 365715 365676 
378427 204 365676 365715 365716 365677 
378428 204 365677 365716 365717 365678 
378429 204 365678 365717 365718 365679 
378430 204 365679 365718 365719 365680 
378431 204 365680 365719 365720 365681 711842 308 676537 676556 677297 677278 676538 676557 677298 677279 
~~~
711843 308 676538 676557 677298 677279 676539 676558 677299 677280 
711844 308 676539 676558 677299 677280 676540 676559 677300 677281 
711845 308 676540 676559 677300 677281 676541 676560 677301 677282 
711846 308 676541 676560 677301 677282 676542 676561 677302 677283 

It seems that there are a different number of nodes per line and some type of identifier in this case 102, 204, 308. What do the 102,204,308 represent? Why this varying of the number of nodes per line? How can I interpret this data in terms of hexahedral elements as a whole?