It is important to set the display format of each instrument appropriately.  If any of your instruments are setup with the incorrect display format, this can cause substantial inefficiencies with respect to both the memory used for each chart as well as the processing of live data.

Right-click in any chart and choose Setup > Instrument and inspect the Format setting. 

You'll see 4ths for instruments that tick in increments of 0.25 and 99.99 for those that tick in 0.01 and 99.9999 for those that tick in 0.0001.  For most instrument, Investor/RT should setup this format correctly automatically, but there are exceptions.  If you're not sure what the correct display format is for your instrument, you can temporarily set the display format to 99.99999 and Apply that setting.  Then right-click on chart and Show > Time & Sales and use the prices shown to clearly determine the tick increment of the instrument (typically the spread between the bid and ask). 

Take this information and go back to Instrument Setup window and set the Format accordingly.

You can inspect the Display Format of all your instruments in one place by opening the All Symbols quotepage and and then adding the Display Format column to the quotepage.  Add the B-A Spread column as well (Bid-Ask Spread).  In general, the information displayed in these two columns should line up.