Misleading vertical axis in foreign exchange graphs analyses?
The convention in finance is that any currency pair "currency1/currency2" is to be interpreted as the number of units of currency2 needed to buy one unit of currency1, or alternatively, as the number of currency2 you get from selling one unit of currency1.

For instance, as of 13th of Match of 2017, the currency pair rate of exchange between the £ and the US $ (GBP/USD) was roughly 1.22. This means that you need 1.22 US dollars to buy £1.

Under this convention, a fall/increase in the GBP/USD means a depreciation/appreciation of the British Pound with respect to the US Dollar.

So, using your example, if the GBP/USD goes up from 3 to 5, then the British Pound appreciates with respect to the US Dollar.

By contrast, the convention in economics is to define the exchange rate as £x/\$1, meaning that you need x British Pounds to buy 1 US Dollar, or that you can sell 1 US Dollar for x British Pounds.

Under this convention, an increase/fall in £x/\$1 means a depreciation/appreciation of the British Pound with respect to the US Dollar.

In other words, the interpretation is exactly the opposite.