Calculation, Constant and Accumulation Tags are limited to a number equal to your IO tag count limit (e.g. if you have a 1200 tag limit, you have 1200 IO tags plus 1200 Internal Tags = 2400 tags).
There is no limit to the local screen tags in WebAccess.
Internal Tags are Calculation Tags, Accumulation Tags and Constant Tags and are globally available to all displays, scripts and other tags. Calculation tags provide arithmetic and logic calculations, similar to a programmable calculator that runs repeatedly using inputs from other IO tags. Accumulation Tags are Totalizers or Integrators (e.g. totalize flow from flow rate). Constant tags are holder tags used for operator entry or to display the results of a script.
Scripts and Displays support the use of local screen tags to store results, read operator inputs and create complex calculations with screen scripts and displays. By using local screen tags in Scripts and Displays you do not decrease your licensed tag count. There is no limit to the local screen tags in WebAccess.
For more information on Tag Limits and "Level" of your license please refer to section 1.5.1 License Tag Limits by Part Number.