Of Equatorial Guinea, Wikipedia states "The eventual treaty of Paris in 1900 left Spain with the continental enclave of Rio Muni, a mere 26,000 km2 out of the 300,000 stretching east to the Ubangi river which the Spaniards had initially claimed.", which lines up with the modern borders of the country. However I can't seem to find any information, or maps, on what the original Spanish claim was. It seems to be implied to have been granted at the Berlin Conference, but all the maps accompanying the topic appear to represent the reality of control at around 1900 rather than the supposed boundaries as stated in 1885.
A brief faffing with the "Measure distance" tool on google maps shows that extending the current eastern border of Equatorial Guinea out until it hits the Ubangi river results in a land area of approximately 47,000km^(2). Still less than a sixth of the original figure given, so the claim must extend either north or south somewhat?
I took a look at the University of Illinois online special collection "Maps of Africa to 1900" and they have a Spanish map from 1889 depicting Spanish claims. Here
However, it looks like a lot of the other European maps do not recognize the Spanish claim and don't even recognize any spanish territory outside of Fernando Po (i.e. no mainland territory between Cameroon and Gabon). This map is pretty typical