It should be "liquidity is calculated as the average of x to y". I am averaging all the numbers in the given rage (e.g. For the short term, that would be the average of -5, -4, -3, -2, -1, and 0). By average, I mean the mathematical mean. Those days represent particular event days. 0 is the main event day. -1 represents one day before the event day etc. The second rephrasing can be used (Liquidity is calculated as the mean of the liquidity on days -5 through 0.
Thank you for all your help.