On SpotGamma models, call delta is the sum of all call option delta (from the perspective of market makers) for all available strikes on all option chains for a given security. 

The primary meaning of delta is directional exposure; nonlinear considerations aside, one delta has the same immediate impact of one share, seven delta is worth seven shares, and so on. Delta also shows the percentage stake of a stock: 39 call delta on a stock means the same instantaneously as being long 39% of a full lot (100 shares) of that stock, and hence 39 shares.

A large total amount of call option delta implies there is a large aggregation of options market maker hedge positions. Some of our levels will pick up on this in various forms, such as the Call Wall or Absolute Gamma, which establish various and reliable forms of support/resistance for high-probability trading setups.